In a large, heavy-bottomed pot over medium heat, add diced bacon or pancetta. Cook for about 5–7 minutes, stirring occasionally, until the bacon is crispy and golden brown. Remove the bacon with a slotted spoon and set it aside.

Season the beef chuck generously with salt and pepper. Increase the heat to medium-high and place the beef into the hot bacon grease, searing it for 4–6 minutes on each side until nicely browned. Remove the seared beef from the pot and let it rest.

In the same pot, add chopped onion, carrot, and celery. Sauté the mixture for about 7–10 minutes, or until the vegetables are softened and the onions become translucent.

Once the vegetables are tender, add minced garlic and red pepper flakes to the pot. Cook for an additional minute, stirring frequently until fragrant.

Pour in the beef broth and crushed tomatoes, then stir in the thyme, rosemary, and Italian seasoning. Return the crispy bacon and browned beef to the pot.

For the stovetop, bring the pot to a gentle boil and then reduce to a simmer, cover tightly, and let it cook for 2–4 hours. For the oven, preheat to 275°F (140°C) and cook covered for the same time.

After cooking, taste the sauce and adjust seasoning with salt and pepper as needed. Make sure to remove bay leaves before serving.