Rinse ham and use a firm kitchen brush to scrub the meat's surface. Transfer ham to a 5-gallon stockpot and cover with cold water. Refrigerate ham in water for 24 hours, changing water every 8 hours.
1 Day in Advance:.
Drain ham and return to stockpot. Add tea and enough water to cover. Soak for 24 hours.
4 Hours Before Serving:.
Drain ham; return to stockpot. Add beer and enough water to cover; bring to a boil over high heat. Reduce heat to medium and simmer until a small knife inserted in the thickest part of the ham slides easily in and out, about 3 1/2 hours.
Heat oven to 400°F.
Drain ham, reserving 1/4 cup of the cooking liquid.
Trim skin and fat; transfer ham to a rack set inside a roasting pan. Whisk together reserved cooking liquid, molasses, brown sugar, and mustard to make a glaze; brush ham with some glaze. Bake ham, occasionally brushing with glaze, until glossy, 15-20 minutes. Let rest for 20 minutes before carving.