In a mixing bowl, whisk together beef broth, soy sauce, oyster sauce, brown sugar, sesame oil, and minced garlic until the brown sugar dissolves.

Take the sliced beef chuck roast and place it in the slow cooker. Pour the sauce over the beef, tossing to coat.

Cover the slow cooker and set it to low for about 90 minutes.

Prepare the cornstarch slurry by mixing cornstarch with cold water until smooth.

After 90 minutes, stir the cornstarch slurry into the slow cooker and add the broccoli. Switch to high and cook for an additional 30 minutes.

Finally, serve the beef and broccoli over rice or cauliflower rice, garnished with sesame seeds or green onions.