In a slow cooker, place the chuck roast and add the bay leaf, garlic, onion powder, onions, thyme, beef broth, and celery seeds.
Cook on low heat for 7-8 hours until the meat is tender.
In a separate bowl, mix cornstarch and water to form a slurry. Add this to the slow cooker along with sugar, oil, Worcestershire sauce, apple cider vinegar, and butter.
Cook for an additional hour until the sauce thickens.
Serve the French Onion Pot Roast hot with your favorite sides.
