The rosette is made from veneer which I glue around a wooden cylinder that has the diameter of the inside of the rosette. The resulting wooden tube is cut to individual rosettes on the table saw. In order to have as little loss as possible, I use a very thin sawblade, the same I use for fret slots as well.
The channel for the the rosette I cut with the router.
After the rosette is installed and the glue is dry it is sanded flush.
Then the top has to be sanded to the desired thickness which is somewhat below 3mm. Depending on how stiff the wood is, it can be a bit more or less.
Finally, the soundhole is cut and the top is ready for bracing.
After resawing the blanks for back, top and sides are about 5mm thick which is ways too much to build a fine instrument.
To make them thinner I use my shop made thickness sander which is basically a table which is attached to a hinge on one side and lies on a bolt on the other side. On top of the table is a metal cylinder coated with sandpaper which is driven by a motor. The cylinder lies parallel to the table and by turning the bolt the gap between cylinder and table can be varied. No rocket science, a pretty straightforward and simple concept which nevertheless works well and with sufficient precision, once you know how to use it.
Before I made that machine I use handplanes to thin the boards which took me about five times longer…
Depending on the wood and part I sand the boards to 3.7 to 2.5mm. Then I join the two halves of the top and the back and glue them together.