The slab furnace is an aesthetic varient of a basic furnace. It is functionally identical to its vanilla counterpart.
It is crafted the same way as a normal furnace, but uses 8 cobblestone slabs instead of cobblestone blocks.
NOTE: You can't actually place two of them in the same block (like regular slabs do).
NOTE: Hoppers don't work properly with the slab furnace as it will pour the items into all three slots even the output slot of the furnace.
NOTE: Unlike normal furnaces, they do NOT create light while smelting.