Let the ham stand 30 minutes at room temperature. Preheat the oven to 325 degrees . Place the ham on a rack set inside a roasting pan. Add 1/3 cup water; cover tightly with foil. Roast until an instant-read thermometer inserted into the ham in several spots (do not touch the bone) registers 140 degrees , 2 to 2 1/2 hours.
Increase the oven temperature to 400 degrees . Generously brush ham with the glaze, if using. Arrange the orange slices on the ham, securing with the cloves; brush them lightly with glaze. Roast until the orange slices brown in spots, brushing occasionally with more glaze, 10 to 15 minutes. Let rest 30 minutes.