Preheat your oven to 300°F (150°C).

Pat the chuck roast dry with paper towels and season it on all sides with salt and black pepper.

In a large oven-safe pot or Dutch oven, heat the vegetable oil over medium-high heat. Once hot, sear the chuck roast for about 4-5 minutes on each side until browned. Remove the roast and set aside.

In the same pot, combine soy sauce, brown sugar, rice vinegar, minced garlic, minced ginger, sesame oil, and red pepper flakes. Stir well to combine.

Return the chuck roast to the pot, ensuring it is submerged in the sauce. Cover the pot with a lid.

Place the pot in the preheated oven and cook for 3 to 4 hours, or until the meat is tender and easily shreds with a fork.

Once cooked, remove the pot from the oven and let the roast rest for 10-15 minutes before slicing.

Serve the sliced roast with the sauce drizzled over the top, garnished with chopped green onions and sesame seeds.