No-fastener solution for picture frames
First, cut a 1⁄8 " groove along the inside edge of the frame material. Then, rabbet deep enough below the groove to accommodate the glass, photograph, and backer board plus approximately 1⁄8 " extra depth for a spacer. After assembling the frame and installing the glass, photo, and backer, fit wood strips into the grooves at each corner of the frame without glue. Finally, make spacers thick enough to fit snug between the wood strip and backer board, and glue the spacers to the strips.
The strips and spacers are easily removed to change the contents of the frame.
—Alex Deaver, Des Moines, Iowa