first type give username minecraft:command _block type this in the commandblock   /summon FallingSand ~ ~1 ~ {id:"FallingSand",Riding:{id:
"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",Riding:{id:"FallingSand",TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-2.175 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"c334ada9-64e6-4a25-8f5a-991840b50d4b\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9qUVdSa0lGLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-3.175 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"5d041c56-b898-41e6-94b6-2e9fa77bf366\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9yS3ZaOXJkLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-3.925 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"4932c0fc-00d0-4df7-beaa-c820e78cfd9a\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9KTlA2aGFxLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-4.925 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"a6cb6bcf-a591-4af9-8da5-03ce2b44f80f\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9wQjBHbFZCLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-5.675 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"f8882774-6d84-45d2-9d5c-85f8d6e54915\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9BdVZKcnYyLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-6.675 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"965f65b9-acf4-4be7-ba8a-7bc28a2a4e87\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9CVEhkbnpiLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.65625 ~-7.425 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"151428a9-8b0b-4dd5-9564-5b0ffbf38aaa\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9ENG9XVTZ0LnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-8.425 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"ab2c5e18-5979-400b-8e47-26782f8bba6f\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9ZU2wxcjVtLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-9.425 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"3ada5ecc-ba32-47c5-8eb5-5dd35fba874f\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9GY3BZeXNLLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.40625 ~-10.425 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"006a05ae-af37-44b8-b8db-00497519a940\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9QbGZmd3NQLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.65625 ~-11.175 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"effdca0d-a2c3-43f7-86a7-66e439503ee7\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9JWkNVeDhXLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-12.175 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"682e61b8-781b-432e-8e99-6dbc64b18b00\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9oMElhNFV0LnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-13.175 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"227f071f-07ae-4c7e-90fa-f338a99a9cee\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS80ZHZqdWZ1LnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.40625 ~-14.175 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"b1504fa6-4568-4c3a-b313-a205bcbcf77a\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9ZS2hWaFlULnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.65625 ~-14.925 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"c77edebd-4d58-4f68-b25e-53e7c7687717\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS96N0FkVmZ2LnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-15.925 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"af56eb43-38a1-45a1-8792-30015ae19cd7\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9DZEV5T0Q2LnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-16.925 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"c64fba42-5356-4238-b2b4-1df599ef7d60\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9yY2oxNXp3LnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.40625 ~-17.925 ~-.125 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"32be57f3-4e19-43fd-b610-3afd48445bc6\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9ycGxqT21LLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-18.675 ~ {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"6b5bc62e-5a64-4547-a490-cd577b0ef87c\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS8xTmtDekMzLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-19.675 ~ {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"524f49ba-5c9c-43e3-95d3-9e543a624b34\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9qSDlyWHhVLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-20.675 ~-.25 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"0045948a-a033-4119-89c8-2d5d8f5e5043\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9ieEV6bXo2LnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-21.675 ~-.25 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"6783cff0-7c14-42fb-acf1-479668ff30bb\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS95RDdERkx1LnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-22.425 ~ {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"e832c6d6-5a83-4867-a10f-b618c2be6e19\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9RY09KWjZuLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-23.425 ~ {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"99496a66-5baf-4f0e-91bd-1291df5d264e\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS9kZXdaRUNtLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~3.90625 ~-24.425 ~-.25 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"752ae57b-e5bc-4f1e-815a-6bfd07be6070\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS82Nk9xTnduLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"/summon ArmorStand ~4.15625 ~-25.425 ~-.25 {Pose:{RightArm:[0.0f,45.0f,0.0f]},Equipment:[{id:\"minecraft:skull\",Count:1,Damage:3,tag:{SkullOwner:{Id:\"145197e8-0b42-4f63-b26f-6c9b06324e5f\",Properties:{textures:[{Value:e3RleHR1cmVzOntTS0lOOnt1cmw6Imh0dHA6Ly9pLmltZ3VyLmNvbS82QnVwZXNxLnBuZyJ9fX0=}]}}}}],NoGravity:1,Invisible:1}"},TileID:137,Time:1b},TileEntityData:{Command:"fill ~-1 ~ ~ ~-1 ~-26 ~ redstone_block"},TileID:137,Time:1b},TileID:152,Time:1b},TileID:1,Time:1b},TileEntityData:{Command:"fill ~ ~1 ~ ~-1 ~-30 ~ air"},TileID:137,Time:1b},TileID:152,Time:1b}