The cost is one Obsidian will make one Obsidian Slab. Image credit: Eurogamer/Epic Games/Lego Once you place a material into the machine it will automatically begin to make Slabs.

You can turn obsidian into obsidian slabs in Lego Fortnite by processing it with the stone breaker. To craft a stone breaker, you need 20 knotroot and 35 marble, which can both be found in Lego ...