This semi-auto design uses hoppers, and is not too difficult to build and is inexpensive. You will need 3 chests, 3 hoppers, and 1 furnace. The raw ingredients for this would be 8 cobblestone, 15 iron ingots, and 12 logs of wood (48 planks). Build instructions [] See below for a step-by-step guide on how to make this semi-auto furnace