The first step after pressing up the panels is to trim the veneer down with a knife in preparation for trimming the panels flush using a router bit. I try to leave about 1/16" overhang on each edge. This will prevent the thin, overhanging veneer from "flapping" against the router bit, which is hazardous both to the operator, and more importantly, the piece.
Trimming the panels with a top-bearing flush-trim bit. This is where using just the right amount of glue pays off - since there is almost no squeeze out, you can use the original panel edge as a bearing surface, rather than planing a new edge by hand.
Cutting the miters on the long edges of the panels. I use an 80-tooth blade made especially for cutting veneered panels. I'd highly recommend one if you do any sort of veneer work - the make accurate cuts, and leave a tearout-free edge.
Ripping the panels down to exact width.
All five sides of the box, laid out and ready for finishing. The three long sides will be joined with miters, and the two smaller end pieces will be attached with butt joints.
Pre-finishing the insides of the box with shellac. Whenever possible, I prefer to finish a piece before it is glued up. This way I have greater access to each surface, and ultimately greater control over the final finish, as there are no nooks or crannies for finish to hide in.
Sealing the edges of the MDF. Because the edges of MDF are so porous, any glue that is applied is sucked up like a sponge. For this reason, I am applying two coats of glue (in this case, extra-slow setting West System epoxy): one coat as a sealer, the second as the actual adhesive.
Gluing up. The trick is to apply even pressure, but not over-tighten the clamps, as this could cause the joints to blow-out.
Checking for square during glue-up.
Assembled Mantel. Next up: Veneering the outside of the box...