1. Preheat oven to 300 degrees F. Using a sharp knife, score the ham with the lines ¼ inch deep and 1 inch apart creating a diamond pattern.
2. Line a rimmed baking sheet with foil. Place the ham, skin side up. On the prepared sheet and cover with foil.
3. Bake until warmed through, 145 degrees F, about 1 ½ hours.
4. Combine the brown sugar, salt, pepper and 2 tbs water in a bowl. Remove the foil and brush the warmed ham with the glaze. Continue to bake uncovered, basting the ham twice with the pan juices, until the skin is golden and glazed, about 30 more minutes.
5. Let rest for 15 minutes before slicing perpendicularly to the bone. Serve warm or at room temperature.