Using a sharp knife or Stanley blade score light incisions into the pork skin along its width, about 5mm apart. Take the salt and rub into the skin and incisions. Place uncovered in the refrigerator for at least 4 hours, to allow the pork skin to dry out and the salt will help extract the moisture from the skin. Do not cover.
Remove from the fridge and allow to come to room temperature.
Pre-heat the oven to 160°C.
Heat a fry pan over a moderate heat, add the oil, wipe any moisture and excess salt from the pork skin and place into the hot pan skin side down, gently brown for about 10 minutes until the skin is golden and crisp.
Place on a rack in a roasting tray and slow roast for 50 minutes, until just cooked and nice and moist in the centre. The cracking will be extremely crispy but light and puffy. Rest in a warm place for 10 minutes and then carve.