Layer the carrots, parsnips, onion, apricots, prunes and garlic in a 5- to 5 1/2-quart slow cooker. Place cinnamon stick, cloves and allspice on the piece of clean cheesecloth. Tie ends together with kitchen twine to form a little bundle. Place pork ribs and spice packet on top of vegetables.
Stir together 1 cup of the chicken broth, the orange juice, balsamic vinegar, salt and pepper in a 2-cup measure until well blended; pour evenly over ribs.
Cover and cook on HIGH for 5 to 6 hours or LOW for 10 to 11 hours, until the vegetables and pork ribs are tender.
Remove ribs to a large platter; cover with foil to keep warm. Remove spice packet.
Stir together remaining 1/2 cup chicken broth and the flour in a 1-cup measure until well blended and smooth. Stir into liquid in slow cooker. Cover and cook on HIGH for 5 to 10 minutes or until liquid is thickened. Spoon vegetable mixture from pot around the ribs on the platter.
Serve with couscous on the side for soaking up the juices, if desired.