In a small bowl, blend sugar, soy sauce, sesame oil, vinegar, ginger, garlic and red pepper.
Place ribs in slow cooker bowl; add sauce. Cover; cook on HIGH for 6 hours or until meat is tender.
Transfer ribs to a platter. Strain sauce and discard excess fat. Combine cornstarch and 1/4 cup water; blend with sauce in a saucepan. Bring to a boil over high heat and cook for 2 minutes, stirring, until thickened. Top ribs with 1/2 cup of sauce, scallions and sesame seeds; serve with remaining sauce.