Heat vegetable oil in a large skillet over medium-high heat. When hot, add the chuck roast and sear on all sides until browned (not cooked through). Remove and place in the slow cooker.
Season the roast with garlic powder, oregano, and black pepper, massaging the seasonings into all sides.
Add the sliced onions and bay leaves around the roast. Pour in the coffee, soy sauce, and Worcestershire sauce.
Cover and cook on LOW for 9 hours. Avoid opening the lid for at least 8.5 hours.
After cooking, remove the lid and discard bay leaves. Take out the roast and place it on a plate; cover with foil. Skim off excess grease from the liquid in the slow cooker.
In a small bowl, whisk together cornstarch and cold water until smooth. Add this mixture to the slow cooker liquid and stir. Cover, turn the slow cooker to HIGH, and cook for 20 minutes until gravy thickens.
Shred the pot roast with two forks. Return shredded beef to the gravy, stir, and let heat through for about 5 minutes.
Serve directly from the slow cooker, garnished with parsley if desired. Best enjoyed with fresh bread to soak up the delicious juices!
