Mix flour with salt and pepper and dredge meat with mixture. Place pot roast and vegetables to crock. Add water to cover. Cover and cook on low 6 to 8 hours. One-half hour before serving, a canned vegetable (green beans, lima beans, etc.) may be added if desired.
If gravy is too thin, turn heat to high and add 2 tablespoons cornstarch dissolved with 1/4 cup cool water during the last half hour. I keep a small pickle jar handy to shake the cornstarch and water together. Flour can be used in place of the cornstarch, but doesn't seem to work as well because the crockpot doesn't quite reach a good boil.