A half hour before your ham is finished baking, simmer together 1 1/2 cups water, raisins, and brown sugar until raisins are plump, about 5 minutes.
In a small bowl, mix together cornstarch and 1/4 cup cold water. Stir into raisin mixture along with the cinnamon. Boil for one 1 minute. Add rum or rum flavoring and bring back just back to the boiling point.
Slice ham. Place on platter and spoon part of raisin sauce over sliced ham. Pour extra sauce in a serving dish. Makes about 2 cups. You may double the recipe if you have a large ham and need more sauce. Enjoy!