Cøzy❤

Hey, I'm quite new to this forum so pardon if I am being an idiot and maybe I've missed some example of how to properly ask these questions but with that out of the way.. I am currently making my first mod and I've tried to look around for how I could have my main block generate with %'s of blocks.. For my biome, I am making a 5 block deep ocean with sand and gravel as the floor with barely any heigh variation, but don't know how to make the floor two blocks and I would really love to have the ability to customize the gravel/sand ratio.. Any help would be appreciated, sorry again if I'm being an idiot..