Toss the lamb shanks in the flour and then shake off any excess. Season with salt and pepper.
Heat 2 tbs of olive oil in a large pot or pan over high heat. Add the lamb shanks and sear for 5 minutes, turning occasionally until brown on the outside.
Place the lamb shanks into the slow cooker and set aside.
Heat the remaining 1 tbs of olive oil in the pan over medium heat. Add the garlic, onion, carrot and celery and cook for 5 minutes or until the onion has softened and is translucent.
Add the red wine, crushed tomatoes, tomato paste, chicken stock, rosemary and the bay leaves and heat to combine.
Pour over the lamb shanks in the slow cooker, trying to submerge them as much as possible.
Cook for 8 hours on LOW.
Serve the lamb shanks with the red wine sauce poured over the top with mashed potato and greens on the side (see notes regarding the sauce).