Step 1: Pat the chuck roast completely dry with paper towels. Season generously all over with 1.5 teaspoons of salt and 0.5 teaspoon of black pepper. Heat olive oil in a large, heavy-bottomed skillet or Dutch oven over medium-high heat. Sear the roast on all sides until a deep golden-brown crust forms, about 3-4 minutes per side. Remove the roast and set aside.
Step 2: Reduce heat to medium. Add the sliced onion to the same skillet, scraping up any browned bits from the bottom. Sauté until softened, about 5-7 minutes. If using red wine, pour it in now, scrape up any remaining bits, and let it simmer for 2 minutes to reduce slightly.
Step 3: Place the seared roast into the slow cooker. Arrange the chopped carrots and potatoes around and over the beef. Pour in the beef broth and the reduced wine (if used). Add the minced garlic, dried thyme, bay leaves, and the remaining 0.5 teaspoon of salt and 0.5 teaspoon of pepper.
Step 4: Cover the slow cooker and cook on low for 7-8 hours, or on high for 4-5 hours, or until the beef is incredibly tender and easily pulls apart with a fork. Avoid lifting the lid frequently to maintain consistent temperature.
Step 5: Carefully remove the roast from the slow cooker to a cutting board. Discard the bay leaves. Shred the beef with two forks or slice it into thick pieces, as preferred. If you desire a thicker gravy, skim any excess fat from the cooking liquid. In a small bowl, whisk together the cornstarch and cold water to create a slurry. Stir the slurry into the hot liquid in the slow cooker. Cook on high for another 15-20 minutes, stirring occasionally, until the gravy has thickened to your desired consistency.
Step 6: Serve the tender pot roast and vegetables with the rich gravy. Enjoy your ultimate slow cooker pot roast recipe!