How it was created:

1. Select "Create New World"
2. Select "More World Options..."
3. Select "Generate Structures: ON" so that it displays "OFF"
4. Select "World Type: Default" so that it displays "Superflat"
5. Select "Customize"
6. Select the top layer and then select "Remove Layer" until all are removed
7. Select "Done"
8. Select "Done"
9. Select "Create New World"
10. Open the Game Menu and select "Open to LAN"
11. Select "Allow Cheats: Off" so that it displays "ON"
12. Quickly type /gamemode creative
13. Double-jump to fly
14. Enter the command /tp 0 64 0
15. Enter the command /setblock 0 63 0 minecraft:grass_block
16. Enter the command /gamemode survival
17. Exit the world
18. Open the save folder%appdata%/.minecraft/saves
    
19. Delete the directories "advancements", "data", "DIM-1", and "playerdata", "serverconfig", and "stats"
20. Delete "level.dat_old" and "session.lock"