Preheat oven to 170 C.
Place oxtail in a plastic bag with flour and salt - shake until oxtail is lightly covered wtih flour.
heat oil in a frying pan and brown oxtail in batches. Pour off fat from frying pan and wipe out any burnt fragments, pour rice wine into the pan and reduce by half. Place oxtail, rice wine, soy sauce, brown sugar, star anise, beef stock, water, ginger, lime leaves, and grated lime in a casserole, cover and cook for 3-4 hours until meat is falling off the bone. Remove meat from the casserole, cover and set aside. Allow liquid to cool and skim off fat as it rises. Check consistency of liquid and reduce if needed. (the sauce shouldn't be too thick)
Meanwhile heat a little oil in a frying pan over a high heat and brown oxtail until crisp. Serve oxtail pieces on steamed rice with greens and ladle over sauce.