Not having built the jig, I thought about the jig Kreg uses to align angles for attaching pocket holes screws. Same principle applies, after you make your compound cut's, Cut complimentary pieces to get you back to 90 degrees and attach them to a piece of plywood creating a mini sled to support the workpiece. Assuming you might want to create more than one compound angle cut for different frames, perhaps building a jig to mount to the router table would work better? I picture a triangle shaped piece of 1/4" Masonite with a hole to fit over your safety pin. This allows you to pivot on the table surface. Useing a straight plunge router bit, plunge slowly up through the Masonite, then pivot your triangle to make a clearance slot for the bit. Mount your biscuit cutter and swing the triangle plate so it shows where the cutter would intersect the edge of the plate. Make a 1/4" rabbit on the 2" edge of 2 pieces of 1"x2". Cut yourself a piece of Masonite 2" x length of the cutter plus 1". By glueing these pieces you will have a zero clearance fence to center along the edge of your triangle plate. Leave at least a 1/2" of the Masonite on the outside of your fence for your workpiece to ride on. Attach it with glue and screws through the bottom. Slowly pivot your plate to cut through your fence to create the zero clearance slot. Now you have a flat surface to hold your mitered piece against. Bring your cutter level with the fence face and clamp it in place. Make a zero mark on your plate at least 3" from the leading edge. Make a matching "reference" mark on the table. A couple of practice cuts on scrap will show you where to mark your stop lines on the plate for different sized biscuits. Now that the jig will function for making cuts, build a small box to cover the cutter for safety. As a bonus this will be a great place to mount a dust collection hose. What do you think of my solution?