You don't have to be a professional to make a solid deer leg gun rack. If you want the rack to look professional, however, you must invest in high-grade equipment. This rack will be a keepsake, meant to last. Buy quality preservatives, mounting forms and taxidermist's clay. These three tools go a long way towards creating a stable, long-lasting rack.
Unless you're planning to buy pre-frozen deer feet, you'll have to dress them yourself. Using strong knives, cut the feet at the knee joints. Peel the skin away from the leg bone to get at the dew claw. Free the claw from the leg along with the tendons. Remove marrow. Coat the legs and hooves liberally with salt. This will draw moisture out from the feet. Pack salt in the leg cavity, as well. Leave for a minimum of 24 hours and a maximum of a month, depending on how long the legs take to dry.
Once your deer legs have been properly treated, it's time for taxidermy. Stuff the leg cavities entirely with taxidermist's clay until they're full and you're satisfied with their shape. Let them set. Choose the length of board the rack will be mounted on and drill two holes in it at the correct distance to hold your gun. When the clay is set, push bolts through the holes on your board and then fit the feet over those bolts. If desired, you can coat your hooves with varnish or black paint to make them stand out.