Place meat in roasting pan and brown uncovered in oven. Season meat with pepper. Dissolve onion soup mix in water. Mix ketchup and beer together and add to soup mixture. Pour mixture over meat. Cover pan with foil and roast for 2 hours or until tender. Add flour to 1/4 cup pan drippings to make a paste. Stir paste into gravy in pan. to make a thicker gravy, add more flour. Return pan to oven and continue roasting for an additional 30 minutes. Slice meat across grain and serve with gravy.