In shallow roasting pan, place ham.
In large saucepan, stir together contents of glaze packet, 2 cups water and the brown sugar; cook over medium heat until sugar is dissolved.
Meanwhile, in small bowl, whisk together remaining 1 cup water and the cornstarch. Add to brown sugar mixture; simmer until mixture begins to thicken slightly. Pour 1/2 of glaze over ham.
Bake ham 1 hour, basting every 10 to 15 minutes. If pan seems to be getting too dry, add small amount of water to pan. Turn oven off. Let ham stand in oven 20 minutes.
Remove excess drippings from pan; stir into remaining 1/2 of glaze. Reheat glaze; serve with ham.