Prepare the Base - Start by placing the sliced onion at the bottom of your slow cooker to create a flavorful base.
Season the Beef - with garlic powder, onion powder, thyme, salt and pepper
Add the Beef - Lay the seasoned beef roast on top of the onions, pressing down to ensure contact.
Pour in the Broth - Pour in the beef broth, Worcestershire sauce, and soy sauce over the beef, ensuring liquids cover at least half of the beef.
Set Up for Cooking - Cover the slow cooker and set it to LOW for 8 hours or HIGH for 4 to 5 hours.
Shred the Beef - Once cooking is done, remove the beef and shred it into bite-sized pieces.
Strain the Broth - Strain the onions from the broth, returning only the liquid back to the slow cooker.
Thicken the Gravy - Mix cornstarch with cold water to create a slurry and stir into broth to thicken.
Serve and Enjoy - Layer mashed potatoes, shredded beef, and ladle gravy over the dish.