Reserve ¾ cup marinade and drain the rest, including garlic and bay leaves. Dry off the beef with paper towels and set aside.
Preheat your oven to 300°.
In a large oven safe pot or Dutch oven, heat olive oil over medium high heat. Add the beef to the pot in batches and sear on all sides, about 1-2 minutes per side. Set beef aside.
In the same pot, add chopped onion and saute for 5-6 minutes, until softened and browned. Add carrots, potatoes, and garlic and saute for another 5-6 minutes, stirring often to ensure the garlic doesn't burn.
Add the beef back to the pot along with the canned tomatoes, beef broth, Worcestershire sauce, ½ cup reserved red wine, ¾ cup reserved marinade, salt, pepper, and rosemary sprig.
Cover the pot and place in your preheated oven and cook for 2 hours, stirring once during cooking, or until the beef and vegetables are fork tender. If the stew is boiling instead of simmering in the oven, lower the heat to 275°.
Remove the stew from the oven and ladle out about ½ cup liquid into a bowl and whisk in 2 tablespoons of flour until smooth. Pour mixture back into the pot with the rest of the stew and whisk until well combined. Simmer for about 3-5 minutes, until stew thickens slightly. Serve immediately.