Sear the beef. In a large cast iron skillet, heat the oil on medium-high heat. Season both sides of the beef roast with salt and pepper, and sear for 4 to 5 minutes on each side to give it a dark brown crust. Transfer the roast to a 6 to 7-quart slow cooker.
Add to slow cooker. Add the garlic, onion, carrots, celery, potatoes, rosemary, thyme, and bay leaves to the slow cooker. Pour the beef broth and red wine on top. Add the lid and cook on low for 8 to 9 hours or on high for 5 to 6 hours.
Remove and shred. Remove the sprigs of rosemary, thyme, and the bay leaves. Then remove the roast and shred or slice it up.
Thicken broth. If you'd like to thicken the broth to more of a gravy consistency, stir together the cornstarch or arrowroot powder and water in a small bowl. Pour it into the slow cooker and stir everything together until it starts to thicken.
Serve. Serve the meat and vegetables on a platter with some of the gravy (you can serve extra gravy on the side)
