Preheat the oven to 220°C/Fan 200°C/Gas 7.
Score the pork rind with a small very sharp knife, making cuts about 1cm apart through the skin into the fat, but not so deep that you cut into the meat.
Rub the salt into the scores, pulling the skin apart a little if needed.
Brush any excess salt off the surface, turn it over and season the underside of the meat with a few pinches of salt and pepper.
Place the pork, skin side up, in a roasting tray and pop in the preheated oven. Roast for 30 minutes, until the skin has started to puff up and you can see it turning into crackling.
Turn the heat down to 170°C/Fan 150°C/Gas 3, cover the pork snugly with a double layer of foil, return to the oven and roast for a further 4½ hours.
Take out of the oven, take the foil off and baste the meat with the fat in the bottom of the tray. Carefully lift the pork up and transfer to achopping board.
Add all the veg, garlic, bay leaves and herbs to the tray and stir them into the fat. Place the pork back on top of everything and return to the stove without the foil to roast for another hour. By this time the meat should be meltingly soft and tender.
Remove from the oven and leave to rest covered with the foil.