Season the chuck roast generously with salt and pepper. Place it in the crockpot surrounded by diced potatoes, sliced carrots, and diced onions.
In a bowl, whisk together beef stock, Worcestershire sauce, minced garlic, garlic powder, onion powder, oregano, thyme, salt, and pepper. Pour over the roast and vegetables.
Cover and cook on low for 7 to 8 hours or high for 6 to 7 hours until the meat is tender.
Mix cornstarch with water to form a slurry; add to the crockpot about 15 minutes before serving to thicken the gravy.
Stir in the sliced mushrooms; cover and cook for an additional 10-15 minutes until everything is heated through.