Cut the beef into large pieces, about 3-4 inches each. Season the beef with salt and pepper. For the best flavor, sear the beef in a heavy skillet until browned on the outside. This skip can be skipped to save time.
In the bottom of the slow cooker, mix together the diced tomatoes, beef broth, red wine, tomato paste, onion, garlic, Italian seasoning, red pepper flakes, bay leaf, salt, and pepper. Once combined, add the beef. Cook on low for 8 hours until beef shreds easily with a fork.