Pour 2-4 cups water in the electric roaster oven, so the bottom of the roaster is covered to a depth of about 1/4 inch. Place the roasting rack in the bottom of the roaster.
Lay 2-3 sheets of heavy duty aluminum foil on a countertop or work surface, overlapping the edges. Use enough foil to cover the entire ham.
Remove the ham from its packaging, reserving any juices. Lay the ham on the aluminum foil on its side, with the cut side facing you.
Lift the foil and wrap it around the ham, leaving the top open.
Place the ham in the roaster on top of the rack. Pour any juices from the packaging over the ham.
Insert the food thermometer probe in the middle of the ham, trying not to touch the bone with the probe. Wrap the top of the ham tightly with the foil, but leave the foil loose enough that you can open it later.
Secure the lid on the roaster, and turn on the roaster to 275 degrees F. Set the probe thermometer to alert when the ham's internal temperature reaches 140 degrees.
Heat the ham to an internal temperature of 100 degrees F (approximately 1 1/2 hours, depending on size). Meanwhile, make the glaze.
Combine all glaze ingredients in a small saucepan, and bring to a boil over medium high heat. Boil glaze for 2 minutes.
When the ham has reached an internal temperature of 100 degrees (approximately 1 1/2 hours), open the foil and pour on 2/3 of the glaze.
Re-wrap the ham, and continue heating until it has reached an internal temperature of 120 degrees (approximately 30 minutes).
Using a pastry brush, brush the remaining glaze on the outside of the ham. Re-wrap the ham and continue heating until the internal temperature reaches 140 degrees (approximately 20 minutes).
Optional: Open the foil and turn the roaster up to 425 degrees F. Bake the ham at 425 degrees for 10 minutes to caramelize the glaze.