Remove ham from refrigerator and allow to set at room temperature for 2 hours.
Preheat oven to 325 degrees Fahrenheit. Remove all packaging from ham and discard. Place ham, flat/cut side down, onto the rack of a roasting pan (or directly into a lined 9x13 baking pan). If using a roasting pan with a rack, pour one cup of water into the bottom of the roasting pan to prevent drippings from burning.
Cover pan with foil and roast until ham reaches an internal temperature of 140 degrees Fahrenheit when a digital thermometer is inserted into the thickest part of the ham, about 12-15 minutes per pound of ham.
Meanwhile, add marmalade, maple syrup, dijon mustard, and cinnamon to a bowl. Stir to combine.
In the last 30 minutes of roasting, remove ham from oven and baste with half of glaze mixture. Lightly tent with foil and return to oven. 10 minutes before ham is done, remove from oven and baste with remaining glaze. Return ham to the oven, uncovered.
Allow ham to rest for 10 minutes before serving.
Plan to serve about ¾ pound of bone-in ham to each person attending.
Leftover cooked ham will keep for 3-4 days in a sealed container in the refrigerator, or for 1-2 months in the freezer.