The rosette...

This rosette is walnut burl surrounded by two strips of Paua Abalone "zip flex". To make the burl part, I used burl veneer and vacuum bag clamped it to a regular piece of walnut (to insure color match if I should sand through). Then the ring was cut out with a dremel in a circle cutting router base.

Then I used the same dremel setup to route the channel in the soundboard. Once that was finished, I carpet taped the rosetted to a piece of plywood, and ran it through the drum sander until is just a little thinner than the channel. This let it sit just below the surface of the soundboard. Then the entire soundboard was sent through the drum sand to make it flush.

The abalone was done similar, but it was left proud and sanded down to the soundboard.