Brown the beef: In a large skillet over medium-high heat, brown the beef on all sides. Remove from the skillet and set aside.

Sauté vegetables: In the same skillet, sauté the onion, carrots, celery, and garlic until softened, about 5 minutes.

Combine ingredients: Transfer the beef, diced tomatoes, beef broth, red wine, Worcestershire sauce, thyme, rosemary, red pepper flakes, salt, and pepper to a slow cooker. Stir to combine.

Cook: Cook on low for 6-8 hours, or until the beef is tender and the flavors have melded.

Add potatoes: Add the potatoes to the slow cooker and cook for an additional 30 minutes, or until the potatoes are tender.

Serve: Serve hot with crusty bread.

Optional additions: For a thicker stew, add a tablespoon of cornstarch mixed with 2 tablespoons of water to the slow cooker. You can also add other vegetables, such as mushrooms or green beans, to the stew.