This guide will teach you how to make a cobblestone generator that you can use when playing skyblock.
Step 1: Dig a Trench
Dig a Trench that looks like the one shown, you should dig out the blocks marked in red.
Step 2: Add Water
Add water to the block marked in blue. It should fall into the hole.
Step 3: Add Lava
Add lava to the far side of the trench, and the water and lava should cool into stone. Once you break the stone, more stone should come back in the exact same spot.
Step 4: Start Mining!
Once your cobblestone generator is ready, you can mine away and mine away, and you'll never run out of cobble. Dig yourself a little hole to stand in, and watch as all your skyblock goals are achieved. Enjoy!