The pork should be unwrapped, dried with a paper towel, and ideally left overnight uncovered in the fridge overnight to dry out thoroughly. Don’t go for small joints which can dry out quickly - go for medium sized ones and eat it over a few days.
Score the skin with a sharp knife and rub salt into the scoring - this will make the crackling crispy. Add herbs if wanted. Sage goes well with pork.
Pork rarely needs any additional fat and basting pork will destroy any crackling. However, if you don’t want crackling then a tablespoon of chilli jelly spread over the joint halfway through will add additional flavour.
Preheat the oven to 245°C, and cook for 20 mins to seal the meat. Then turn down the temperature to 190°C and cook for 70 mins per kilo (pork leg) or 60 mins per kilo (pork shoulder).