To make the stuffing, combine apple, raisins, fennel, paprika, garlic, oil and salt.
Untie the pork belly and lay it on a board skin-side down. Place the stuffing along the skinless side, putting the extra piece of pork on top of the stuffing. Roll tightly and tie with kitchen string. Pat the skin dry and rub with olive oil and salt.
Cook in roasting pan for 30 minutes or until skin starts to crackle, rotate halfway through cooking to help crackling crisp evenly. Reduce oven to 180°C (fan forced 160°C) and roast for a further 1 hour or until meat juices run clear. Rest for 15 minutes, carve and serve.