Pat the chuck roast dry with paper towels and season generously on all sides with salt, pepper, and paprika. Heat olive oil in a large skillet over medium-high heat until shimmering.

Sear the roast for 3-4 minutes on each side until a deep golden-brown crust forms. Transfer the seared roast to your slow cooker.

Layer the sliced onions around and on top of the roast in the slow cooker. Add the minced garlic, carrots, and celery chunks around the meat.

In a mixing bowl, whisk together beef broth, red wine, tomato paste, and Worcestershire sauce until well combined. Pour this mixture over the roast and vegetables.

Add the dried thyme and bay leaves to the slow cooker. Cover with the lid and cook on LOW for 8-10 hours or HIGH for 5-6 hours, until the beef is fork-tender and shreds easily.

Carefully remove the roast from the slow cooker and transfer to a cutting board. Shred the beef using two forks, discarding any large pieces of fat.

Strain the cooking liquid through a fine-mesh sieve into a large measuring cup, pressing on the solids to extract maximum flavor. Reserve the caramelized onions separately.

To make the gravy, melt butter in a saucepan over medium heat. Whisk in flour and cook for 1-2 minutes until golden. Gradually whisk in 3 cups of the strained cooking liquid, stirring constantly until the gravy thickens, about 5-7 minutes.

Return the shredded beef and caramelized onions to the gravy, stirring to combine and heat through. Season with salt and pepper to taste.

Serve the pot roast over creamy mashed potatoes, spooning extra gravy over the top. Garnish with fresh parsley and enjoy!