Heat oven to 325Â°. Line a roasting pan with foil. Wrap the ham in foil, keeping the ham fat side up; place it in the baking pan.
Bake for 18 to 20 minutes per pound, or until a meat thermometer or temperature probe registers about 145Â°.Meanwhile make the glaze. In a medium saucepan, combine brown sugar, cinnamon, flour, mustard, and vinegar. Stir over medium-low heat until smooth. Add water and bring to a simmer. Simmer, stirring, for 1 minute.
Remove the foil from the ham and remove excess fat. Score the ham all over the surface, creating a diamond pattern. Return to the oven and continue baking to about 155 to 160Â°, basting with the glaze mixture frequently.