Preheat the oven 220°C/gas 7.
Lay the pork joint flat, cutting the string and unrolling if necessary.
Mix together the Chinese five spice and the salt. Rub all over the pork, making sure it gets into the cuts in the rind. Place the pork on a rack over a roasting tin.
Roast for 20 minutes then reduce the oven to 170°C/gas 3 for a further 120 minutes until the pork is thoroughly cooked and the juices run clear. Leave to rest for 5 minutes.
Cut the belly pork into chunks, and serve with stir fried greens.