Pat the beef chuck roast pieces dry with paper towels. Season all sides generously with 3/4 tsp salt and 1/4 tsp black pepper.

Heat 1 tablespoon olive oil in a large skillet or Dutch oven over medium-high heat until shimmering. Sear the beef pieces for 3-4 minutes per side, until deeply browned. Do this in batches if necessary to avoid overcrowding the pan. Remove the beef and place it in the bottom of your 6-quart or larger slow cooker.

Reduce the heat to medium. Add the chopped onion, carrots, and celery to the same skillet. Sauté for 5-7 minutes, stirring occasionally, until softened.

Add the minced garlic and tomato paste to the skillet. Cook for another 1-2 minutes, stirring constantly, until fragrant and the tomato paste has darkened slightly.

If using, pour in the red wine and deglaze the pan, scraping up any browned bits from the bottom. Let it simmer for 2-3 minutes until the liquid has reduced by about half.

Transfer the sautéed vegetables and any remaining liquid from the skillet to the slow cooker, on top of and around the beef.

Pour in the crushed tomatoes, diced tomatoes (undrained), and beef broth. Add the remaining 1/4 tsp salt, 1/4 tsp black pepper, dried Italian seasoning, red pepper flakes (if using), and bay leaves. Stir gently to combine the liquids and seasonings around the beef.

Cover the slow cooker and cook on LOW for 7-9 hours or on HIGH for 3.5-4.5 hours, or until the beef is incredibly tender and easily shreds with a fork.

Once cooked, carefully remove the bay leaves. Use two forks to shred the beef directly in the slow cooker, or remove the beef to a cutting board, shred it, and return it to the pot. Stir the shredded beef into the rich sauce. The sauce will thicken as it cools slightly.

Taste the ragu and adjust seasonings if necessary.

Serve hot over cooked pasta (like pappardelle, fettuccine, or tagliatelle), polenta, creamy mashed potatoes, or even crusty bread. Garnish with freshly grated Parmesan cheese and chopped fresh basil or parsley, if desired.