Place the trimmed and sliced beef into the base of the slow cooker.
In a small mixing bowl, whisk together the soy sauce, brown sugar, minced garlic, grated ginger, sesame oil, red pepper flakes, and beef broth.
Pour the sauce mixture over the beef and stir until all pieces are thoroughly coated.
Secure the lid and cook on low heat for 6 to 8 hours, or on high heat for 3 to 4 hours until the beef is fork-tender.
Approximately 10 minutes before serving, cook the noodles in boiling water according to package instructions until al dente.
Drain the noodles and incorporate them directly into the slow cooker, tossing with the beef and sauce to combine.
Garnish with sliced green onions and sesame seeds before serving.