Heat th oil in a 12-inch skillet over medium-high heat until hot. Add ribs to skillet and sprinkle with salt and pepper to season. Cook ribs about 10 minutes or until well browned on all sides, turning occasionally.
Meanwhile, in 5- to 6-quart slow-cooker , place potatoes, onion, carrots and celery. Salt and pepper to taste.
Transfer ribs to slow cooker on top of vegetables. Add garlic.
In the same skillet used to brown ribs, add beef broth and gravy mix and heat until mixed well. Pour over ribs and vegetables in slow cooker.
Cover slow cooker with lid and cook on low setting for 8 to 10 hours (or on high setting 4 to 5 hours) or until meat is fork-tender and falling off the bones.
Using tongs, transfer ribs to deep platter; discard bones if you like. With spoon, skim fat from sauce in slow cooker and discard fat. Spoon vegetables and sauce over ribs.