Lay pork shoulder, skin side up, on a chopping board. Using a sharp knife, carefully score the skin at 1 cm intervals. Be careful not to cut completely through the fat, as the meat can dry out if you do.
Place the salt and five spice powder in a small bowl and toss together to combine. Rub two-thirds of the salt mix into the skin and scores. Flip the pork over and rub the remaining salt mix into the flesh.
Transfer the pork, skin side up, to the baking tray or a plastic container large enough to hold it when laid flat. Refrigerate, uncovered, for at least 6 hours (or overnight), as this helps the skin dry out.
When ready to cook, preheat the oven to 160°C. Remove the pork from the fridge and set it aside for 20 minutes, to come to room temperature. Transfer the pork if necessary to the baking tray and roast it for 31⁄2 hours. If the skin starts to burn on the edges, cover those areas with tinfoil.
After the 31⁄2 hours, increase the oven temperature to 200°C and roast for a final 30 minutes, or until the crackling puffs up slightly and makes a hollow sound when tapped. Remove the pork from the oven and set it aside, uncovered, to rest for 20 minutes while you make the slaw. The crackling will continue to harden while resting.
Finely slice the wombok, widthways, then transfer to the large mixing bowl. Cut the apples in half top to bottom, then slice thinly, discarding the core. Stack the slices and cut them into matchsticks. Add the apple to the wombok, along with the peanuts.
Finely slice the chilli into rounds and add them to the slaw. Pick the coriander leaves. Leave a few aside for garnish, then roughly chop the rest and add to slaw. Pour in the vinegar and oil, then, with clean hands, mix salad ingredients to combine. Season with salt and pepper to taste, and garnish with the extra coriander leaves.
Serve the pork on a board, carving thick, generous slices at the table. Serve the slaw on the side.