Dig a straight trench 5 blocks long and 1 block wide
Place 1 water source at one end of the trench
Place 1 lava source at the opposite end of the trench
Leave the middle blocks empty so the water and lava meet
Place a block at the end of the trench to stop the water from flowing away
Mine the cobblestone that forms where the water and lava meet
Replace any broken source blocks if needed
Use a pickaxe to collect the cobblestone faster
Add a second water and lava setup beside the first for faster production
Build a safe wall or barrier around the generator to prevent falling into the lava