Usually, those stock medallions are inset into the stock. That requires drilling or cutting a shallow hole for the medallion, then a smaller center hole for the pin and whatever accommodation is required for a nut on the inside. Things can get complicated when, as with most S&W wood stocks, the nut is a large stamped piece that fits closely into the cutout in the frame, so that any error in placement cannot be easily corrected.
The best approach is to bypass the stud and nut entirely and simply use epoxy or a cyanoacrylate ("crazy") glue to fix the medallion in place. The recess will still have to be cut of course, but that is a relatively easy job, with either a modellers knife (X-Acto) or a Dremel tool. With care and fitting, a very neat job can be done in a few minutes.
Jim