MMfoto, I've been searching online and asking a similar question here, recently.
I'm trying to restock some frames that I purchased years ago. They're plain, light wood, ready made, standard sizes (mine are 16x20). Everything, glass, matted and mounted print and backing board, drop in from the back. The entire perimeter of the frame has a groove in the surface that's perpendicular to the backing board. Spring clips, like the ones that hold things in place in metal frames, are used *across* the corners, ends set into the groove, with the curved middle portion providing tension across the corner of the backing board.
Are you familiar with these or can you recommend something similar? They're easy to re-use and require no tools.