Step-by-step
Preheat the oven to 240°C/Gas 9. Place the pork on a board and pat the rind dry with kitchen paper if it feels at all damp. Mix the thyme with the salt and pepper and rub this seasoning mixture into the pork rind and the underside of the pork.
Place the pork in a sturdy roasting tin or flameproof baking tray and roast for 25–30 minutes. This will give the rind a chance to bubble and become really crisp. Turn the oven down to 180°C/Gas 4 and continue roasting for another hour.
Toss the apples with the onions, whole sage leaves and a few twists of black pepper. Make a compact pile in the centre of a clean, smallish roasting tin. When ready, remove the pork from the oven and place it on top of the apples and onions, keeping the apple and onion pieces snugly underneath the meat so they don’t burn. Keep the first roasting tin to one side because you’ll need the cooking juices to make the gravy. Return the pork to the oven and cook for a further hour until the meat is really succulent and tender.
Take the first roasting tin, skim off any fat from the cooking juices and place the tin over a medium heat. Stir in the flour and cook for a minute or so, stirring constantly. Gradually stir in the cider and 100ml of water and bring to a simmer. Cook for 3–4 minutes, while stirring. Strain through a sieve into a small saucepan and season to taste. Set aside.
When the pork is cooked, transfer it to a carving board. Scoop up the apple and onion with a large spoon and place in a warmed serving bowl. Reheat the cider gravy until bubbling and cut the pork into thick slices. Serve the pork and crackling with the apple and sage and the hot gravy.