Routing the rosette channel
Dremel rotary tools attract criticism from some quarters due to their questionable robustness (this one is my third), but when combined with one of Stew-Mac's soundhole jigs and their router base, they're well suited to the task and I'm able to achieve a near-perfect fit of the rosette and the adjoining purfling rings. If there's a secret to success, it's in exercising patience and "sneaking up" on the final channel width in tiny increments, checking the fit of the rings after each cut until they slip into the channel with light pressure.
Dry-fitting the rosette and purfling rings
Once the rosette has been glued in place and allowed to dry, I feed the top through my drum sander until the rosette and the rings are at the same level as the top. I can easily check when I've arrived at that point by holding the top at an angle such that the the scratches left by the sander are clearly revealed against the light from the workshop door. I want to see continuous scratches along the full length and across the full width of the top, including the rosette. Once that's achieved, I bring the top to the desired thickness using the drum sander to remove material only from its inner face.
The zebrano rosette - glued and levelled
Click on any of the images for a closer look.