Preheat your oven to 300°F (150°C).
In a bowl, whisk together honey, soy sauce, apple cider vinegar, minced garlic, grated ginger, black pepper, salt, and red pepper flakes until well combined.
Place the scored pork belly in a baking dish and pour the marinade over it, ensuring the pork is well coated. Cover the dish with aluminum foil.
Bake in the preheated oven for 2.5 to 3 hours, or until the pork is tender.
Remove the foil and increase the oven temperature to 425°F (220°C). Brush the pork belly with sesame oil and bake for an additional 20-30 minutes, or until the skin is crispy and caramelized.
Once done, remove from the oven and let it rest for 10 minutes before slicing.
Garnish with chopped green onions and serve.