Yup, a mounting plate is the easiest way to go.
No, you don't need to route a place for the plate, but... the plate is ~1/16" thick, so the top of the plate will be that far above the top of the rest of the CP. Covering with an overlay won't hide that (and if done wrong you can get wrinkled or torn or warped art work). Routing the 1/16" off the top of the CP for the plate isn't too hard, and doesn't have to be perfect if you cover it (gaps between plate and CP can be filled with putty).