Tie each shank with kitchen twine. Toss in flour, salt and pepper.
Heat oil in a heavy pan. Brown shanks 3 minutes per side. Tip into slow cooker.
Same pan, cook onion, carrot, celery 10 minutes. Add garlic 1 min. Tip into cooker.
Add wine to pan, boil 2 minutes. Pour into cooker. Add tomatoes, stock, rosemary, bay.
Cover. Cook on low 7 hours (or high 4 hours) until meat is fork-tender.
Combine gremolata ingredients in a small bowl.
Serve shanks over saffron risotto or soft polenta. Top with gremolata.