Preheat the oven to 375 degrees F (190 degrees C). For meatballs, combine ground beef, green onions, ginger paste, garlic, chili flakes, sesame oil, and soy sauce in a shallow bowl.
Line a sheet pan with parchment. Scoop out mixture 1 tablespoon at a time and roll into balls. Place on the prepared sheet. Once all meatballs are formed, place the sheet in the refrigerator.
For glaze, add Hoisin sauce, soy sauce, rice vinegar, honey, and Chinese 5 spice to a small saucepan. Over medium low heat, bring to a slight simmer, stirring constantly until thickened. Remove from heat and stir again. Reserve half the sauce in a small dish for a dipping sauce; the other half of sauce will be used for glaze.
Place meatballs in a deep casserole dish. Pour the beef stock over meatballs.
Bake meatballs in the preheated oven for 10 minutes. Remove from the oven and turn all the meatballs over. Return to the oven for 5 more minutes. Remove meatballs from the oven; brush with glaze using a pastry brush. Roll meatballs to coat on all sides. Return to the oven and bake for 3 minutes more to solidify the sauce.
Remove from the oven. To serve, place rice on a plate; ladle over some of the broth. Add meatballs on top, and sprinkle with sliced green onion and sesame seeds. Serve with reserved dipping sauce.
