Trim any excess fat from the roast then season it generously with salt and pepper.
Add the oil to a large skillet set over medium-high heat. Once the oil is hot, add the chuck roast and sear it on all sides then transfer it into an 8-quart slow cooker.
Reduce the heat to medium. Add the onions and garlic to the skillet and cook for 1 minute. Add the red wine and cook, scraping up any brown bits, for 1 minute. Pour the onion mixture into the slow cooker.
Add the bay leaves, thyme, carrots and potatoes around the roast. Pour in the beef broth then cover the slow cooker and set it to LOW for 8 hours or HIGH for 4 hours. (Cooking time will vary based on the size and thickness of the roast.)
Once the roast is tender, remove it from the slow cooker and shred it. Remove the vegetables to a serving platter.
Transfer the cooking liquid to a medium saucepan set over medium-high heat. (You can strain the liquid first before transferring it, or transfer it as is.) Whisk in the cornstarch mixture and bring the sauce to a boil until it thickens enough to coat the back of a spoon, about 3 minutes. Alternately, you can skip the cornstarch and serve the liquid as an au jus.
Serve the pot roast with vegetables and gravy.