Preheat the oven to 300°F.
Place ham in a large roasting pan, fat-side up. Score the ham with cuts across the skin, about 2-inches apart and 1/2-inch deep. Then cut diagonally down the previously made slashes to form a diamond pattern. Season with salt and pepper.
Place sage in a bowl with the oil, mixing to make a paste. Rub the sage-oil all over the ham and into the slits.
Bake the ham for 2 hours.
While ham is baking, add all ingredients for the glaze to a saucepan and place over medium heat. Slowly cook the liquid down until syrupy; this should take about 30 minutes.
After the first 2 hours of baking, top the ham with the tangerine glaze. Continue to cook for 1 1/2 hours more, basting with juices every 30 minutes until ham is dark, crispy, and glistening with a sugary glaze.
Set the ham on a cutting board to rest a few minutes before carving.