For the marinade: Place all the ingredients except the juice in a large mortar and pound to a paste with a pestle. Stir in the bitter orange juice. If desired puree these ingredients in a blender or food processor. Set aside.
For the pork: Trim the skin only from the back of the leg. Wipe the leg of pork clean. Make several deep incisions all around the leg, except for the skin. Rub with salt. Allow to rest for a few minutes. Rub pork all over with the marinade, pushing it in the deep gashes made all over the leg. Cover with plastic film and refrigerate, preferably overnight or for a couple of hours. Wipe the marinade from the skin with a clean cloth.
Cooking the pork: Preheat oven to 400 degrees F.
Place the leg on a roasting pan. Bake uncovered with the skin side up for about 4 hours. Check the roast often, add some orange juice, and water if the pan juices dry out. Cook until the skin is like a crackling and the juices run clear when the meat is pierced on the thickest part of the leg (about 160 degrees F on a meat thermometer), about 3 1/2 hours