Thoroughly pat the beef chuck roast dry on all sides using paper towels. In a small bowl, combine coarse kosher salt, cracked black pepper, garlic powder, and onion powder. Rub the spice blend evenly over the entire surface of the roast, pressing firmly into the crevices.

Heat 2 tablespoons of oil in a large cast-iron skillet or enamel Dutch oven over medium-high heat until shimmering. Carefully lay in the chuck roast and sear undisturbed for 4 to 5 minutes per side, developing a deeply caramelized, mahogany golden-brown crust. Transfer the seared roast onto a plate.

In the bottom of a 6-quart slow cooker (or Crockpot), layer the onion wedges, smashed garlic cloves, carrots, and baby Yukon gold potatoes to create an aromatic vegetable roasting trivet.

Place the caramelized chuck roast directly on top of the root vegetables. Pour the seared beef pan drippings over the roast.

In a measuring pitcher, whisk together beef bone broth, tomato paste, Worcestershire sauce, and Dijon mustard. Pour the liquid around the edges of the beef into the slow cooker. Tuck fresh rosemary sprigs, thyme sprigs, and bay leaves into the broth around the roast.

Cover with the lid and cook on LOW for 8 to 9 hours (or on HIGH for 5 to 6 hours) until the beef yields completely to a fork and pulls apart like butter.

Gently transfer the tender roast, carrots, and potatoes to a warm serving platter and tent loosely with foil. Discard the herb stems and bay leaves.

Skim off excess fat from the surface of the cooking liquid, or pour the braising juices through a fat separator. Pour 2 cups of the strained juices into a small saucepan over medium-high heat. Whisk in the cornstarch-water slurry and simmer for 2 to 3 minutes until thickened into a glossy, velvety brown herb gravy.

Shred the succulent beef into generous rustic chunks, ladle the bubbling herb gravy generously over the meat and vegetables, garnish with minced fresh parsley, and serve piping hot.