The violin method is to carve the center longitudinal arch to a template, then the center latitudinal and then work in bands around it. From the outside you now have a very nice shape. Set up your drill press with a rounded peg like a beefed up contact on a micrometer. Now make the space between a 1/4" or smaller bit and the peg your thickest graduation for the plate. Rough out the plate. Draw the pattern of your graduations now (usually thickest in the middle) and set it to slightly thicker than the next thickness, proceed to do the same. If you practice you can make this work down to about .5mm. You must have a very stable press. So the exterior carving takes some time, but the inside can be roughed out accurately pretty quickly.