"This ham is to die for. Sounds to difficult to make but it is very simple. I serve this dish during Easter or Christmas, or whenever I'm in the mood for ham. The flavors of the Dijon mustard and the brown sugar are intensified with the orange rum. Igniting rum will help glaze the ham and melt any remaining sugar, plus it looks cool, too."
Place ham into a roasting pan. Spread Dijon mustard over top and sides of ham in an even coat; sprinkle ham with brown sugar. Press brown sugar onto ham with your hands. Place pineapple slices onto ham, securing them to the top and sides with cloves. Place any unused pineapple slices into bottom of roasting pan and pour pineapple juice and half the orange-flavored rum.
Bake in the preheated oven until ham is heated through and brown sugar has begun to glaze onto the meat, about 1 hour. Remove ham from oven and pour remaining 2 fluid ounces of orange rum over the ham; carefully light the rum on fire with a match. The flames will help the glaze to adhere to the meat.
Continue baking until an instant-read meat thermometer inserted into the thickest part of the ham, not touching bone, reads at least 140 degrees F (60 degrees C), about 1 more hour. Let ham rest for 10 minutes before serving. Transfer ham to a serving platter, leaving pan drippings in roasting pan.
Stir cornstarch and water together in a small bowl until smooth; whisk cornstarch into pan drippings. Place roasting pan over medium-low heat and whisk until pan juices thicken, about 5 minutes. Serve with ham.