Place pork, skin-side up, on a wire rack set over a baking tray. Sprinkle with 1 tsp salt. Chill, uncovered, overnight to dry skin.
The next day, preheat oven to 220 ̊C. Dry skin with paper towel, then scatter 1 tsp salt over skin. Bake for 1 hour or until skin is crisp. Combine chipotle chillies, adobo sauce, tomato paste, sugar and 11/2 cups (375ml) water in a jug. Line a baking dish with foil and pour in chipotle sauce. Place pork, skin-side up, on top of sauce. Reduce oven to 160 ̊C. Roast for 1 hour 45 minutes or until tender. Remove from oven. Set pork aside, discarding sauce. Cool slightly.
Meanwhile, to make the pickled onions, combine vinegar, sesame oil and 1/2 tsp salt in a bowl. Add onion, then cover with plastic wrap and set aside to pickle.
For the gochujang mayonnaise, combine all ingredients in a bowl. Chill until needed.
To make the slaw, combine the cabbage, jalapeno and coriander in a bowl.
Thickly slice pork. Spread tortillas with gochujang mayo. Top with slaw, pork, onion and coriander. Serve with lime wedges.