Lift pot roast to a hot platter. Skim fat from juices in roasting pan, add water to juices to make 1 1/2 cups. Put 1/2 cup cold water into shaker, add 4 tablespoons of flour, shake well. Stir into juices, cook, stirring constantly, until gravy is bubbly. Season with salt and pepper. Simmer 2-3 minutes. Makes 2 cups.