- Dig a 3x3 whole
- place 9 obsidian in that whole
- place a furnace at the front and 7 obsidian leaving the middle open
- place 3 obsidian in front 3 in back
- surround the furnace in cobblestone stairs leaving the corners and front of the furnace open
- finish by placing a sign and typing [Lavafurnace] include the brackets
- You can add chest to the furnace to allow for mass smelting, left is the input chest right is the output. Place them in the front two corners.
- Putting lava buckets into the receiving (left) chest will automatically replenish the furnace upon depletion.