reheat the oven to 220C/425F/Gas 7.
Pat the pork belly dry with kitchen paper and score the skin with a sharp DIY knife, easier to ask your butcher to do this for you.
The scoring should be right across the width of the meat, in parallel lines close together. The scoring should go through the skin, into the fat, but not into the meat below.
Finely chop together the rosemary leaves, pepper and salt. Rub the pork all over with the sunflower oil before rubbing the herb and salt mixture into the skin, pushing it in between the scored lines.
Roughly slice the carrot and onion place in the roasting tin with the star anise and cranberries. On top of this place the pork skin-side up and cook for 35-40 minutes or until the skin starts to puff and go crisp.
Turn the oven down to 160C/325F/Gas 3 and roast for a further 3 hours checking every so often to ensure the tin is not dry. If dry add a small amount of liquid.
After 3 hours add the liquid to the tin and turn the oven back up to 220C/425F/Gas 7 and cook the pork for another 20 to 30 minutes, or until the skin is crisp.
Keep warm while you use the liquid in the tin for your gravy.