The frame and panel back fitted and installed in the case.

 

The panel was constructed so that it was a little over sized in both length and width. Then it was carefully trimmed on the tablesaw and jointer to achieve a tight fit in the case's back opening. The rabbets in the case sides and top were 3/4 inches deep. The back panel was constructed so that it ended up being 11/16 inches thick. This allowed the panel to sit in the rabbets with the top and back edges about a 16th of an inch strong. This exposed lip was planed flush with the back panel for a clean sharp appearance.. Then the back was cleaned up a beltsander and orbital sander. STB