In a bowl mix together the gochujang, light soy sauce, sugar, gochugaru (Korean chili flakes), black pepper, salt, garlic, ginger, and sesame oil. Then set aside.
Next, add in the sliced pork belly, sliced yellow onion, and green onions to the mixture. Stir everything until the pork is covered in the sauce, then marinate it for 15 minutes.
In a large pan heat 1 tbsp of cooking oil over medium heat then add in the pork. Cook the pork for about 3-5 minutes until the pork has cooked through.
Serve over white rice and garnish with extra green onions, then enjoy!