The bowl shown above was turned from a flat piece of wood IE: a board. I developed this technique so that bowls could be turned from rare woods without having to find blanks. This simple technique involves the cutting of rings on the lathe. Variations in segments and materials can be used as shown in the last two pictures. Even plastic bowls are possible. Note: Unlike conventional ring cutting techniques this method does not require you to buy a new machine and it does not put ugly HOLES in your bowls.
The “Bowls From Boards” book describes the technique and associated tooling!
Why would you want to turn a bowl from a flat board?