Heat olive oil in a large sauté pan over medium-high heat until shimmering but not smoking. Pat your chuck roast dry with paper towels to help achieve a good sear, then season liberally on all sides with kosher salt and freshly cracked black pepper.
Add the seasoned roast to the hot sauté pan, searing it on all sides (including edges) for about 4-5 minutes per side until browned beautifully.
Without wiping out the pan, reduce heat to medium and toss in sliced onions along with a couple pinches of salt and pepper, stirring occasionally until softened (about 4 minutes). Then add smashed garlic, tomato paste, brown sugar, Italian seasoning, garlic powder, onion powder, chili powder, plus additional salt and pepper; cook briefly to combine flavors.
Pour Worcestershire sauce into your sauté pan alongside a few splashes of beef stock to deglaze by scraping off those tasty browned bits stuck to the bottom; this is essential as it adds layers of flavor! Transfer this onion-garlic mixture into your slow cooker along with carrots, potatoes, and pour in remaining beef stock before adding more salt and pepper generously.
Nestle fresh thyme sprigs, rosemary sprigs, and bay leaves among the veggies so that their flavors meld perfectly during cooking time! Cover your crock pot's lid securely; set it on high heat (cooks for approximately 5-6 hours) or low heat (around 8-10 hours) until roast is fork-tender enough to shred effortlessly.