While sgraffito involves scratching away a layer of engobe, you can also carve away entire slices of clay from your piece to create an interesting relief. The advantage is that you often don’t need to extensively glaze your work.
Carving symmetrical shapes does require some preparation. It is best to outline what you are going to do. You can do this with an ordinary pencil, because those lines will simply burn away in the kiln. Just make sure that the object you are going to carve has a thick enough wall, because otherwise you might end up going through it…
