One Command: New Flat World

summon FallingSand ~ ~3 ~ {Block:redstone_block,Time:1,Riding:{id:FallingSand,Time:1,Block:command_block,TileEntityData:{Command:"/fill ~1 ~0 ~0 ~1 ~-13 ~0 redstone_block 0 replace"},Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"setblock ~1 ~3 ~ stone"},Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"setblock ~ ~4 ~ command_block 0 replace {Command:\"fill ~ ~ ~ ~1 ~-15 ~ air\"}"},Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"scoreboard objectives remove neveruse"},Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"tp @e[score_neveruse_min=1] ~ -200 ~"},Riding:{id:FallingSand,Block:command_block,TileEntityData:{Command:"scoreboard players set @e[type=FallingSand] neveruse 0"},Time:1,Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"scoreboard players set @e[type=!Player] neveruse 1"},Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"scoreboard objectives add neveruse dummy"},Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"replaceitem entity @p slot.hotbar.2 redstone_block"},Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"replaceitem entity @p slot.hotbar.1 command_block"},Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"replaceitem entity @p slot.hotbar.0 diamond_sword"},Riding:{id:FallingSand,Block:command_block,Time:1,TileEntityData:{Command:"gamerule doMobSpawning false"},Riding:{id:FallingSand,Time:1,Block:command_block,TileEntityData:{Command:"gamerule doDaylightCycle false"},Riding:{id:FallingSand,Time:1,Block:command_block,TileEntityData:{Command:"gamerule commandBlockOutput false"}}}}}}}}}}}}}}}}