Before there were vanilla flat worlds, players had to use mods, map editors, and plugins to create them. CleanroomGenerator, despite not changing for over a year, still has a better feature set than most of them. It’s got an elegant configuration method. You append the generator line with the layers of materials you desire. (eg. CleanroomGenerator:5,wool:2 creates 5 magenta wool layers) Simple, works, useful. We use this on our server to generate all air blocks on custom and Alpha.