Step 2: Making the Frame - 1
The first step is to figure out the desired inside dimensions of the frame. I chose to allow enough room for two rows of three, 4"x6" pictures. I made the inside of the frame 20" wide by 10" tall to allow for some extra room around the pictures. Make your first 45° cut at one end of the molding, making sure that the cut is in the proper orientation. From the inside corner of the cut just made, measure out your desired inner length dimension and make the second 45° cut. Continue until all four piece are cut. Ensure that the opposing sides match by using the first to measure the cut for the second. Once cut, lay out the pieces and check the fit. Make any adjustments now.
Cut the 1/2" x 3/4" furring strip into lengths a couple inches longer than each of the four sides. Use wood glue to attach these to the back of each piece of the frame making sure that the furring strip is longer than the frame piece on both ends. Clamp these to the frame and let them dry. Once dry, I further secure them with finishing brads. If using brads, use a small punch to drive them in order to avoid hitting the frame with a hammer. The small holes from the heads can be filled with wood filler if desired.
Finally, cut the excess furring strip flush with the 45° cut of the frame on all 4 frame pieces.