Leaving ham’s inner plastic or foil covering intact, place ham in large container and cover with hot tap water; set aside for 45 minutes. Drain and cover again with hot tap water; set aside for another 45 minutes.
Adjust oven rack to lowest position and heat oven to 250 degrees. Unwrap ham; remove and discard plastic disk covering bone. Place ham in oven bag. Gather top of bag tightly so bag fits snugly around ham, tie bag, and trim excess plastic. Set ham cut-side down in large roasting pan and cut 4 slits in top of bag with paring knife.
Bake ham until center registers 100 degrees on instant-read thermometer, 1 to 1 1/2 hours (about 10 minutes per pound).
Remove ham from oven and increase oven temperature to 350 degrees. Cut open oven bag and roll back sides to expose ham. Brush ham with one-third of glaze and return to oven until glaze becomes sticky, about 10 minutes (if glaze is too thick to brush, return to heat to loosen).
Remove ham from oven, transfer to cutting board, and brush entire ham with another third of glaze. Let ham rest, loosely tented with foil, for 15 minutes. While ham rests, heat remaining third of glaze with 4 to 6 tablespoons of ham juices until it forms thick but fluid sauce. Carve and serve ham, passing sauce at table.
To Make Maple-Orange Glaze: Combine all ingredients in small saucepan. Cook over medium heat, stirring occasionally, until mixture is thick, syrupy, and reduced to 1 cup, 5 to 10 minutes; set aside.
To Make Cherry-Port Glaze: Simmer port in small saucepan over medium heat until reduced to 2 tablespoons, about 5 minutes. Add remaining ingredients and cook, stirring occasionally, until sugar dissolves and mixture is thick, syrupy, and reduced to 1 cup, 5 to 10 minutes; set aside.
Step-by-Step: How to Keep a Ham Moist.
A big ham can take hours to heat through in the oven, by which time the meat becomes very dry. We found two tricks for reducing oven time and increasing moisture retention. Wrapping: Cooking the ham in an oven bag reduces the oven time by another half hour or so. Soaking: Placing the wrapped ham in warm water for 90 minutes raises its internal temperature and decreases the cooking time by over an hour.