01 - Preheat the oven to 320°F.
02 - Combine soy sauce, honey, hoisin sauce, brown sugar, rice vinegar, sesame oil, ketchup, garlic, ginger, chili flakes, and black pepper in a bowl; whisk until smooth.
03 - Place ribs in a roasting dish and pour half the marinade over the ribs, turning to coat evenly; reserve the remaining marinade.
04 - Cover the dish tightly with foil and bake for 2 hours, turning the ribs once halfway through.
05 - Transfer reserved marinade to a small saucepan and simmer over medium heat for 6 to 8 minutes until slightly thickened. Set aside.
06 - Remove foil from ribs; increase oven temperature to 400°F. Brush ribs generously with the thickened glaze.
07 - Return ribs to the oven, uncovered, and roast for 20 to 30 minutes, basting once or twice, until sticky and caramelized.
08 - Transfer ribs to a platter and sprinkle with sesame seeds and sliced spring onions before serving.