[NOT SOLVED] Help with making custom biome almost completely flat (I am open to using custom code)

So, I am trying to make a biome that is completely flat, with only 1 block of variation, and no hills, or any of that sort of stuff. I have tried setting both the biome base height and the biome height variation to 0, but this doesn't seem to work. I still get hills and lots of height variation. I am open to using custom code, and I am using the most recent version of MCreator (not including snapshots). If anyone knows how to fix this, I would love some help.