Preparation of Chuck Roast: Season both sides of the chuck roast generously with kosher salt and freshly ground black pepper. In a large skillet, heat two tablespoons of olive oil over medium-high heat. Once the oil is hot, add the chuck roast and sear it on both sides until a brown crust forms. Upon completion, transfer the seared roast to the slow cooker.
Cooking of Onions and Garlic: Utilize the same skillet and reduce the heat to medium. Add the quartered onions and sauté them until they are browned on the edges. Subsequently, reduce the heat to low, add the coarsely chopped garlic, and cook for an additional minute, ensuring constant stirring to prevent burning.
Creating the Cooking Liquid: Pour in the beef broth into the skillet. If opting to use dry red wine, add it at this stage along with the Worcestershire sauce, chopped rosemary, thyme, and bay leaves. Stir the mixture well, ensuring the incorporation of all ingredients.
Initial Cooking Phase: Transfer the liquid mixture from the skillet to the slow cooker containing the chuck roast. Set the slow cooker to high and cook for 2 hours.
Adding Vegetables: After the initial 2 hours, add the carrots and baby yellow potatoes to the slow cooker. Continue cooking on high for an additional 2 to 3 hours, or until the vegetables and roast are tender.
Finalizing the Dish: Carefully remove the chuck roast and vegetables from the slow cooker and place them on a cutting board, covering them loosely with aluminum foil. In a small bowl, whisk together the cornstarch and water until smooth. Gradually whisk this mixture into the liquid in the slow cooker. Cover and cook on high for an additional 10 minutes to thicken the gravy.
Serving: Slice the chuck roast against the grain and serve alongside the cooked vegetables. Pour the thickened gravy over the meat and vegetables as desired.