01 - Heat olive oil in a large skillet over medium-high heat. Sear beef cubes on all sides until browned, working in batches if necessary. Transfer browned beef to the slow cooker.
02 - In the same skillet, add onion, carrots, and celery. Sauté for 3-4 minutes until softened. Add garlic and cook for 1 minute more. Transfer vegetables to the slow cooker.
03 - Add crushed tomatoes, tomato paste, red wine, beef broth, oregano, basil, thyme, bay leaf, and red pepper flakes to the slow cooker. Season generously with salt and pepper. Stir to combine all ingredients.
04 - Cover and cook on low for 8 hours, or until beef is very tender and shreds easily with minimal resistance.
05 - Remove and discard the bay leaf. Use two forks to shred the beef directly in the sauce. Taste and adjust seasoning with salt and pepper if needed.
06 - Serve ragu hot over cooked pasta or polenta. Garnish with fresh chopped herbs and Parmesan cheese if desired.