With the hopper you can produce an automatic oven in Minecraft, which will work constantly, during your absence. It is enough to place the Furnace at a certain height. Then, at the bottom, top and sides install hoppers and additional boxes and a box by the hopper below.
Thus you put more resources from the top to melt/burn. Fuel is also supplied from the side, and it can also be a bucket of lava - after emptying the bucket, it will be transferred to the lower tray. In the box below you will be able to collect the processed materials.
One bucket of lava is ~12 parts of carbon.
When putting the hopper down hold down the Shift key and place it next to the object instead of activating the object. Always place the hopper by pointing the cursor at a specific object: the tip of the funnel should be directed to the location to which the raw material is brought.