Heat a skillet over medium-high heat. Add oil to pan; swirl to coat. Add onion and celery, carrot, thyme and garlic; cook 10 minutes or until vegetables are tender. Scrape onion mixture into a 6-quart electric slow cooker. Add hocks, beans and stock. Cover and cook on LOW for 8 hours or overnight.
Remove hocks from pan; cool slightly. Remove meat from bones; discard fat, skin, and bones. Chop meat; stir into beans. Cook 10 minutes to allow flavors to meld. Sprinkle with chives and black pepper.
