Place picnic ham on a large roasting pan or baking dish, fat side up. Pour 3/4 cup of water into the bottom of the baking dish.
Cover roasting pan with foil and bake in the oven for 1 hour. This allows the rind to be removed easily.
Remove the foil and peel the rind off the top of the fat cap. Cut cross check slits into the fat and about 1/2 inch into the meat of the ham.
Puree remaining ingredients (oranges, brown sugar, vinegar, honey, mustard, cinnamon, salt and cayenne) in a blender to make the glaze. Brush some of the glaze all over the ham, making sure to get into the slits.
Bake for another 2 hours, uncovered. Brush the glaze after 1 hour cooking time and then again about 30 minutes later. Bake the remaining 30 minutes.
Once done cooking, the fat should be starting to crisp and the glaze nicely caramelized. Let the ham rest for about 5 minutes before carving.
Carve the ham into nice sized serving slices. Serve with glazed carrots, potatoes, squash and more!