01 - Season beef chunks evenly with salt and black pepper.
02 - Heat a large skillet over medium-high heat and sear the beef chunks on all sides until browned, about 5 minutes total, to develop flavor.
03 - Place chopped onions, minced garlic, diced carrots, and celery into the bottom of the slow cooker.
04 - Arrange the seared beef chunks atop the vegetable mixture in the slow cooker.
05 - Pour crushed tomatoes, red wine, tomato paste, and beef broth over the beef. Sprinkle in oregano, thyme, bay leaves, remaining salt, pepper, and red pepper flakes if desired.
06 - Gently stir the ingredients to combine without shredding the beef.
07 - Cover and cook on low heat for 8 hours or on high heat for 5 hours until the beef is very tender and shreds easily.
08 - Discard the bay leaves. Use two forks to shred the beef directly in the slow cooker and mix well to incorporate with the sauce.
09 - Taste the sauce and adjust salt and pepper as needed.
10 - Serve hot over cooked pasta or creamy polenta, garnished with chopped fresh basil or parsley and grated Parmesan cheese if desired.