Think of it like a panel cabinet door. The cutting tools and process can be the same. Or you can purchase panel moulding from your local trim supply and use 3/4 ply as the stiles and rails and 1/4 ply as the panel and trim out with the moulding. No real process, other then keeping the openings as symmetrical as possible. Base and shoe moulding on the floor and crown on the cieling. You may do the cieling as trayed.