In the diagram below I have drawn (not very accurately) an oval bowl, but it can be almost any shaped provided the space between lines is always the same.
If you extend straight lines to the edge of the wood and then draw lines across the thickness of the wood you can determine what the bowls wall thickness will be at this spacing (don't forget make it a bit thicker than you want to allow for sanding. You can also determine here what angle you need to set the scroll saw table to.
Once all the pieces are cut stack them up and glue them together minus the bottom piece.