Pat chuck roast dry and season with salt and freshly ground black pepper all over. In a large skillet or dutch oven over high heat, heat oil until shimmering. Brown beef on all sides until a deep brown crust develops, about 7 to 10 minutes. Transfer beef to slow cooker.
In the same skillet, add carrots, onions, and potatoes and cook stirring occasionally, until vegetables begin to brown, about 5 minutes. Add garlic and cook until fragrant, about 30 seconds. Stir in red wine, deglaze pan by scraping up brown bits.
Add beef broth, tomato paste, thyme, bay leaf, 1 teaspoon salt and 1/2 teaspoon freshly ground black pepper and bring to a simmer. Transfer mixture to slow cooker. Cover slow cooker and cook on low until meat is fork-tender, about 5-8 hours. Remove beef and vegetables (discard bay leaf). Keep warm while making gravy.
To make the gravy, pour drippings into a bowl. Allow fat to rise to the top. Spoon off fat and reserve 1/4 cup (discard any excess). In a large saucepan over low heat, pour in reserved fat. Whisk in flour and cook until golden brown, about 1 minute. Set aside to cool.
Measure remaining meat juices and add water until it reaches 2 cups liquid. Add mixture to sauce pan, return to medium-high heat and bring to a boil, stirring constantly. Boil until mixture thickens, about 1 minute. Season to taste with salt and pepper (I like 1/2 teaspoon salt and 1/4 teaspoon pepper). Transfer to a serving platter or serve the pot roast with vegetables right from the slow cooker.