Preheat the oven to 240°C.
Dry the pork skin and rub both sides with a mix of thyme, salt, and pepper.
Roast the pork in a flameproof baking tray for 30 minutes until the skin is crisp.
Reduce the oven temperature to 180°C and roast for one more hour.
Combine the apples, onions, sage, and pepper in a roasting tin.
Place the pork on top of the apple mixture and roast for one more hour.
Skim fat from the first tray and stir in flour over medium heat for one minute.
Whisk in the cider and 100ml of water, then simmer for 4 minutes.
Strain the gravy through a sieve and season as desired.
Slice the pork and serve with the apple mixture and hot cider gravy.