Cut ribs into serving sized pieces. Coat meat evenly with mixture of flour, salt and pepper using paper bag method.
Melt in heavy skillet the shortening and add ribs. Brown slowly on both sides. Preheat oven to 350°F.
While meat is browning, Mix into stock ketchup, Worcestershire sauce, vinegar, celery salt, cayenne pepper, cloves, allspice, bay leaf and garlic. If using vegetable stock, add 6 tbsp Worcestershire sauce instead of 3 tablespoons.
Put meat into roasting pan and pour stock mixture over browned ribs. Add onion to pan.
Cover and bake at 350°F for about 1 1/2 hours or until ribs are tender.
With a slotted spoon, remove ribs and onion from pan onto a warm serving platter. Set platter back into cooling oven.
Skim excess fat from cooking liquid and strain cooking liquid into small saucepan.
Put into a 1 pint screw-top jar 1/4 cup cold water and the 2 tbsp flour. Cover jar tightly and shake until mixture is well blended.
Bring liquid in saucepan to boiling, stirring constantly. Slowly pour one half flour liquid into saucepan stirring constantly. Bring back to boiling. Add remaining flour liquid as needed to make desired consistency. Bring to boil after each addition. Cook 3 to 5 min additional.
Taking the platter from oven, spoon or pour half of sauce over ribs and onions and serve remaining sauce as gravy.