Remove ham from refrigerator and bring up to room temperature. Preheat oven to 250F and place oven rack at the lowest position.
Once ham has come up to room temp, tightly wrap the ham in foil, transfer to the oven and bake 1 1/2 hours, until the internal temperature reaches 100F. (The ham has already has been cooked so dont be afraid of the internal temperature only reaching 100F.)
Meanwhile, prepare the glaze: In a medium-size saucepot, add the rest of the ingredients and bring up to a boil. Stir to fully dissolve the brown sugar and reserve.
When the ham has reached an internal temp of 100F, remove the foil wrapping and brush with 1/3 of the glaze. Cook 10 more minutes. Remove from oven and glaze again with 1/3 of the remaining glaze and let rest for at least 15 minutes.
Serve up the spiral ham with the remaining glaze at the table. If the glaze is too thick, add some of the juices from the ham.