In a slow cooker, combine soy sauce, brown sugar, honey, sesame oil, garlic, ginger, and red pepper flakes. Stir until well mixed.

Add the sliced flank steak to the slow cooker, ensuring the meat is well coated with the sauce.

Cover and cook on low for 6-8 hours or on high for 3-4 hours, until the beef is tender.

Once cooked, shred the beef with two forks and stir it back into the sauce.

Serve the Korean beef over cooked rice, garnished with chopped green onions and sesame seeds.