Preheat the oven to 200C/400F/Gas 6.
Rub the oil all over the skin of the pork loin, then rub in sea salt, to taste.
Place the pork into a roasting tin and cook for 20 minutes, then reduce the heat to 180C/350F/Gas 4 and cook for a further 1 hour 20 minutes, or until the pork is cooked through and the fat is crisp. Use a meat thermometer to make sure the meat is thoroughly cooked.
When the pork is cooked through, spread the honey all over it, then set aside on a warm plate to rest.
Using a sharp knife, cut the crackling from the pork loin.
To serve, carve the pork into four thick slices and place each inside a burger bun. Drizzle the apple sauce over the pork and add a piece of crackling to each bun.