Step 1. Prep the glaze. Preheat your oven to 325°F (162°C) and adjust the rack to the lower position. In a mixing bowl, whisk together the apple cider, brown sugar, mustard, and honey until smooth.
Step 2. Pour and cover. Place the ham, cut side down, in a large roasting pan. Pour the glaze evenly over the top, separating the slices slightly to let it seep in. Cover the pan tightly with aluminum foil to lock in the steam.
Step 3. Bake. Bake for 10-12 minutes per pound. For an 8-pound ham, this will be about 1 hour and 20 minutes to 1 hour and 30 minutes.
Step 4. Caramelize. Remove the foil and carefully turn the ham onto its side. Continue baking uncovered for another 30 minutes, basting with the pan juices every 10 minutes to build a sticky crust.
Step 5. Rest. Once the ham is golden and heated through, remove it from the oven. Let it rest for at least 10 minutes before slicing to keep the juices locked in.