Mash cranberry sauce with a fork. Stir in sugar, cranberry juice, mustard and cloves.
Place the pork roast in a large roasting pan. Pour cranberry sauce mixture over the roast.
Cook at 275 F for 6 to 8 hours (until the meat is tender). Remove the roast and keep warm.
Skim the fat from the liquid in the roasting pan. Pour 2 cups of the remaining roasting liquid (add water if necessary) into a small saucepan.
Bring the mixture to a boil over medium-high heat. Blend cornstarch and cold water to make a paste. Gradually stir the cornstarch mixture into the boiling liquid. Continue cooking, stirring constantly, until the mixture thickens. Add salt to taste and serve with the roast.