Don’t slice the ham before reheating. It turns into a pile of dry, cold shreds. Do score the surface (cut shallow diamond patterns) to let the glaze seep in. Don’t use a high oven temp—patience is a virtue, and ham respects patience. Do let the ham rest for 10-15 minutes after coming out of the oven. This lets the juices settle down. You wouldn’t run a marathon and then immediately collapse—neither should your ham.
One more thing: if you’re reheating a ham that says “fully cooked” but has a spiral cut, be extra gentle. Those slices are already separated, so they dry out faster. Wrap that sucker in foil plus a layer of plastic wrap before the oven. Trust me, I’ve learned the hard way.