1. Preheat oven to 325°F. Trim off ham rind to expose thick layer of fat underneath. Use a sharp knife to score fat in a diamond pattern, making sure to not cut all the way through. Press 1 clove into center of each diamond. Place ham in a large roasting pan and pour in 2 cups of water. Cover loosely with foil and bake until heated through, about 18 minutes per pound (2 hours 25 minutes for an 8-lb. ham).
2. Make glaze: Combine molasses, mustard, lemon juice and butter in a small saucepan. Stir over medium-high heat until butter has melted and mixture is blended.
3. Remove ham from oven and brush entire ham with about 1/4 of glaze. Return ham to oven and continue baking, uncovered, until a meat thermometer inserted into thickest part of ham reads 160°F, about 45 minutes. Brush with remaining glaze every 15 to 20 minutes of baking time.
4. Transfer ham to a work surface and loosely cover with foil. Let stand at room temperature for 15 to 20 minutes before thinly slicing.