- To brine the ham, combine 4 quarts cold water, 1 cup salt, and the garlic, onion, peppercorns, coriander, bay leaves, and parsley in a container that is large enough to hold the ham, and stir until salt is dissolved.
- Submerge ham in liquid and refrigerate for at least 24 hours and up to three days. (Alternatively, if you can’t fit the ham in your refrigerator, brine it directly in a clean cooler, just adding a little extra salt and enough ice to keep the ham cold, draining a little brine and adding more ice as needed.)
- Preheat the oven to 350 degrees.
- Drain ham, discarding all brine and seasonings. Pat ham dry. Put ham on top of a paper towel lined cutting board so that it doesn’t slip. Using a sharp knife, score skin with incisions that run the length of the ham and are about ½-inch apart, and then again the other way to form a crosshatch pattern. Incisions should just barely reach into fat under the skin; do not cut into meat itself, in order to help crackling skin stay in one piece once it is crispy. Allow ham to come to room temperature.
- Lightly oil and salt meat, rubbing it in on all surfaces. Place ham on roasting rack or on a few rolled-up sheets of aluminum foil in large heavy roasting pan, and put it in oven. A 15-pound roast will take almost four hours to roast, while an 18-pound ham will take as long as five hours— about 15 minutes per pound. After roasting 2½ hours, when temperature of the ham hits about 130 degrees, raise oven temperature to 425 degrees to crisp the skin (cover any areas that start to get too dark with a piece of foil). When meat thermometer reads 145° to 150°F, remove from oven and allow it to rest, loosely tented with foil, for an hour or so before carving.