Here are a couple of pics of the top thickness being graduated. Larry does this after routing for the binding, but before installing the binding.
Larry taps the top, listens, and decides how much will be taken off the edge of the lower bout based on how the box is responding. A slot of the proper depth is routed in the edge, and then sanded ("fared" or "faired"?) into the surface of the top. The result is a wedge shape, thickest in the middle, with continuous thinning toward the edge.
On this guitar, Larry took .008" off the edge. This may seem insignificant, but I can attest is makes a huge different in the responsiveness of the box.