Preheat oven to 140°C/120°C fan-forced. Using a sharp knife, cut and discard pork rind, leaving a thin layer of fat. Combine garlic powder, cumin, paprika, salt flakes, pepper, oregano, orange and lime zest, lime juice, 1 tbs orange juice and 1 tbs oil in a small bowl.
Heat remaining oil in a large frying pan over medium-high heat. Cook pork, turning, for 10 minutes or until browned all over. Transfer to a roasting pan. Brush all over with spice mixture. Add stock and remaining orange juice to pan. Cover tightly with foil. Bake for 3 hours 30 minutes or until tender.
Remove pan from oven and carefully uncover. Increase oven to 180°C/160°C fan-forced. Bake for a further 30 minutes, turning pork halfway through, or until pork is golden and very tender.
Meanwhile, to make the spicy citrus salsa, place reserved lemon juice and eschalot in a small bowl. Stand for 10 minutes to pickle. Combine lemon, orange and lime segments in a bowl. Add chilli, coriander, eschalot mixture and oil. Season and toss to combine.
Transfer pork to a large plate. Using 2 forks, shred pork. Drizzle over with a little of the pan juices. Serve with salsa and tortillas.