3;1*minecraft:bedrock,4*minecraft:water,5*minecraft:stone,6*minecraft:air,60*minecraft:stone,1*minecraft:grass,60*minecraft:air,1*minecraft:stained_hardened_clay:15;5;village,mineshaft(chance=0.01),stronghold(chance=32 count=3 spread=3),biome_1(distance=32),dungeon,decoration,lava_lake 

It's a 1 block thick layer of black clay, with taiga villages on top. Under it, there's a strange, dark world that is pretty much like normal flatlands, only dark with lava lakes and bits of adandoned mineshaft poking out the surface. Under that, there's a thick layer of stone and ores, and under that, there's a small space with strange gravel heaps and precious ores in the floor. Under that, it's a water world with gravel heaps.

So yeah, what cool superflat presets do you like?