At least two hours before cooking the pork, remove it from its packaging, dry thoroughly with a paper towel and return it to the fridge, uncovered to dry out.
Pre-heat the oven to 475F / 245C.
Take a very sharp knife and score the skin of the pork. You want it to cut the skin but not go all the way through. The better your skin is scored, the better the crackling will be.
Lay the rosemary and thyme sprigs onto the bottom of a large roasting tin.
Peel and slice the garlic and lay it on top of the herbs.
Now place the pork on top of the herbs.
Right before you put it in the oven, sprinkle the skin of the pork with at least 1 tablespoon of salt.
Place the roasting tin into the hot oven and cook for 20 minutes at this temperature.
Then turn the temperature down to 375F / 190C and leave the pork to cook undisturbed for a further 35 minutes per pound (450g) of meat. So for a 3lb / 1.5kg leg of pork, this will be for a further 1 hour and 45 minutes.