Combine beef and ham with milk, eggs, onion, bread crumbs, salt, allspice, and pepper. Shape into meat balls about 2 inches in diameter. (If desired, meat balls may be smaller.) Carefully arrange meat balls in slow-cooking pot. Cover and cook on low for 2 1/2 to 3 1/2 hours. Turn control to high. Stir in flour that has been dissolved in 1/4 cup water. Add catsup and dill weed. Cook on high for 15 to 20 minutes or until slightly thickened. Turn heat off; stir in sour cream.