How do you make a cobblestone generator in minecraft?

It's very simple, and one of the main objectives on skyblock. First, you need 1 bucket of lava, and 1 bucket of water (or block of ice). Dig a 1x4 hole, and dig one of the middle blocks in that hole. Place the water or ice on the block closest to the hole you made in the middle (break the ice block). Next place the lava on the opposite side. Now admire what you have created.