Preheat the oven to 220°C / 425°F / Gas mark 7.
Prepare a roasting tin with foil and set aside.
Using a very sharp knife score the skin all over, taking care not to cut through to the meat (you can as your butcher to do this).
Drizzle the pork skin with a little olive oil and then massage one tablespoon of salt into the skin forcing it into the score marks.
Put the onions and carrots into a large roasting tin, drizzle with olive oil and mix around to coat.
Sit the pork on top of the vegetables and place into the oven.
Cook for half an hour, or until the crackling is crisp and golden-brown.
Turn the oven down to 180°C / 350°F / Gas mark 4.
Baste the pork with the juices from the bottom of the pan and cook for 30 minutes per kilo, or until the pork is just cooked through (the juices will run clear when pierced with a knife.
Baste regularly as the pork cooks.
In a pan filled with 50ml of water, add the apples.
Cover and cook over a medium low heat for five minutes or until the apples have started to break down a little and soften.
Add 1-2 tablespoons of sugar and cook for a further five minutes stirring occasionally until the apples are collapsed but there is still a little texture.
Taste and adjust the sweetness if necessary.
Leave to cool to room temperature.
Once the pork is cooked remove from the oven and leave to rest covered in foil for 15-20 minutes.
Serve the pork and crackling sliced with the apple sauce on the side and roast potatoes.