Creating Ocean map, with islands vastly scattered about in a small radius

I'm completely new and like actively learning while trying to cook up what I'm trying to cook up. But essentially I'm trying to make a recreation of Klinbee's survival islands datapack, but just compress it so it functions the same in that the whole world is ocean and it spawns islands everywhere, but compress it to treat 1000x1000, as if it's the entire world. So just a bunch of islands of decent size relative to the radius of the border.
I'm just super lost, I've been going at this for so long and would appreciate any guidance or help here. I feel like it'll probably be pretty easy but I'm just bashing my head against a wall here.