Creating Slow Cooker Korean Beef is as easy as following these simple steps:

1. Prepare the Beef: Cut the beef chuck roast into 1-inch pieces. Trim any excess fat if necessary.
2. Mix the Sauce: In a bowl, combine soy sauce, brown sugar, rice vinegar, sesame oil, minced garlic, grated ginger, and crushed red pepper flakes (if using). Mix well.
3. Add Ingredients to Slow Cooker: Place the beef pieces in the slow cooker. Pour the sauce mixture over the beef, ensuring all pieces are well-coated.
4. Add Beef Broth: Pour in the beef broth to add flavor and moisture to the dish.
5. Cook: Cover the slow cooker and set it to low for 6-8 hours or high for 3-4 hours. Cook until the beef is tender and easily shreds with a fork.
6. Optional Thickening: If you prefer a thicker sauce, mix cornstarch with a little water to create a slurry. Stir it into the slow cooker about 30 minutes before serving and allow it to thicken.
7. Shred the Beef: Once cooked, remove the beef from the slow cooker and shred it with two forks. Return it to the sauce in the slow cooker and stir to combine.
8. Garnish: Before serving, sprinkle chopped green onions and sesame seeds over the beef for added flavor and presentation.

These steps will guide you in creating this incredible dish effortlessly.