Pat 2kg of rolled beef chuck roast dry and season all over with 1 teaspoon of salt and 1 teaspoon of black pepper.
Heat 2 tablespoons of olive oil in a large skillet over high heat. Brown the beef well on all sides, about 7 minutes, then transfer it to a slow cooker.
Cook 1 chopped onion and 5 minced garlic cloves in the same skillet until the onion softens. Add 1 cup of dry red wine, simmer until reduced by half, and pour over the beef.
Pour 3 cups of low-sodium beef broth into the slow cooker, keeping back 1 cup. Whisk ⅓ cup of all-purpose flour into the reserved broth until smooth and stir it in.
Add 5 carrots and 3 celery stalks, cut into chunks. Sprinkle in 1 teaspoon of dried rosemary and 1½ teaspoons of dried thyme, cover, and cook on low for 5 hours.
Add 750g of potatoes, cut into chunks, and cook for 3 hours more, until the beef and vegetables are tender.
Rest the beef for 5 minutes, then slice it. Season the gravy with salt and pepper and spoon it over the beef and vegetables.
