First, in a slow cooker, add chuck roast to crockpot.
Next, add all ingredients listed in Korean Beef Sauce Mixture and sliced onions. Do not add slurry at this time.
Cover crockpot with lid and cook on low for 6-8 hours, or until beef can easily be shredded and/or tender.
Once beef has thoroughly cooked, shred beef, then add slurry mixture. (this will help the sauce thicken)
Turn heat down to warm setting, and let it simmer for additional 30 minutes.
Serve over rice and vegetables.
