Preheat your oven to 300°F (150°C).
In a bowl, whisk together soy sauce, hoisin sauce, brown sugar, rice vinegar, sesame oil, garlic, ginger, black pepper, and red pepper flakes until well combined.
Place the chuck roast in a large oven-safe pot or Dutch oven. Pour the marinade over the roast, ensuring it is well coated.
Add the beef broth to the pot, covering the roast halfway.
Cover the pot with a lid and place it in the preheated oven. Cook for 3 to 4 hours, or until the roast is tender and easily shreds with a fork.
Once cooked, remove the pot from the oven and let the roast rest for 15 minutes before slicing.
Serve the sliced roast with the cooking liquid spooned over the top. Garnish with sliced green onions and sesame seeds.