Pat the beef chuck roast thoroughly dry on all sides using paper towels (dry meat creates an optimal Maillard sear). In a small ramekin, mix kosher salt, black pepper, garlic powder, and onion powder. Season the roast aggressively on every facet, pressing the spices firmly into the meat.

Heat 2 tablespoons of oil in a large heavy cast-iron skillet over medium-high heat until faintly smoking. Add the roast and sear undisturbed for 4 to 5 minutes per side, including the narrow edges, until a deep mahogany caramelized crust forms. Transfer the seared roast to a plate.

Reduce the skillet heat to medium. Add tomato paste and smashed garlic cloves, stirring constantly for 60 seconds until fragrant and brick-red.

Pour in 1 cup of beef bone broth, Worcestershire sauce, and balsamic vinegar. Scrape up all the rich browned caramelized bits (fond) stuck to the skillet bottom with a wooden spoon. Whisk vigorously, bring to a gentle simmer for 2 minutes, then remove from heat.

Scatter the thick onion wedges, carrot chunks, and baby potatoes evenly across the bottom of a 6-quart slow cooker (this creates an aromatic vegetable trivet that prevents the roast from resting directly on hot ceramic).

Nestle the seared chuck roast directly on top of the root vegetables. Pour the warm deglazing broth and remaining 1 cup of beef bone broth over the meat. Tuck fresh rosemary sprigs, thyme sprigs, and bay leaves around the sides.

Cover with the lid and cook on LOW for 8 to 9 hours (or HIGH for 5 to 6 hours) until the beef is exquisitely fork-tender and effortlessly pulls apart with zero resistance.

Carefully transfer the tender beef chuck roast and root vegetables to a warm serving platter with tongs; tent loosely with aluminum foil to keep hot. Discard the spent herb stems and bay leaves.

Skim excess fat from the slow cooker cooking juices. In a small bowl, whisk cornstarch and cold water until smooth. Whisk the slurry into the slow cooker juices, switch to HIGH setting for 10 to 15 minutes (or transfer to a small saucepan over medium-high heat on the stovetop) until the gravy turns glossy, luxurious, and coats the back of a spoon.

Gently pull the beef into large, juicy succulent chunks using two forks. Ladle the hot savory onion gravy generously over the shredded roast and vegetables, garnish with fresh thyme leaves, and serve immediately!