Fitting the Mitered Rails
When it comes to fitting mitered corners, no matter how large or small, I wish I knew some magic tricks. I don’t. My method is to make a few test cuts on scrap to dial my miter saw carefully to 45°, then mark and cut the pieces one at a time. I tend to work my way around a frame so I can cut and fit each joint in sequence. The last corner is never easy, but make the fourth rail a hair longer than needed, and creep up on the final joint with your miter saw or with a disc sander.
Spread glue on both the rabbets and the edges of the frame base, and install the moldings with clamps. I have a small band clamp with corner fixtures that make this job a whole lot easier! I clamped up the entire assembly at once and adjusted the corner fixtures as needed until the joints closed properly.
Finishing Things Up
My puzzle’s frame stock is curly maple. To “pop” the figure, I sanded the wood up to 400-grit and wiped it with boiled linseed oil. It really accentuates the depth. Once the oil dried, four coats of spray lacquer wrapped the project up. Now, all I have left to do is give this puzzle away … that is, after I assemble it a few times myself.