You can i am actually in the process of making such an island base on a plain biome so i can farm on top of that. It's kinda huge and i need tons of rocks though. I'm running out now. As for the method to get rocks you could either make a greydwarf farm (i used to have 3 of them in an old save) or find gigantic rocks and break their base (either in the mountain biome or plain biome) so that the rocks will actually break entirely you will get tons of rocks, though my PC is kind of in the weaker side so it actually crash when i do it sometimes.

I don't recommend doing a greydwarf farm for farming rock even though you can afk and get lots of drops from them you still need to tames wolves and hope they don't die due to sneak attacks and that your wolf breeders don't run out of meat or that the the greydwarf spawner get destroyed somehow (that happenned twice when i did it).