Custom Height for Cave Biomes

 I want to make a magma cave biome that will generate at the bottom of the world in the deepslate layer. I tried to find any kind of setting to do that but didn't find any. I went to the forums to see if anybody has the same question. From all i found, "Base height" used to be a thing but people say it was removed. My question is if it is still possible to make a biome only generate at the bottom of the world since setting the biome to a cave biome seems to mostly put it around y = 0