Pat the 3 lb beef chuck roast dry with paper towels, then season all sides evenly with 1 tsp kosher salt and 0.5 tsp black pepper.

Heat 2 tbsp olive oil in a large skillet over medium-high heat, then sear the roast for 3 to 4 minutes per side until deeply browned before transferring it to a 6-quart crockpot.

In the same skillet, add 1 large sliced yellow onion and 4 minced garlic cloves, sauteing for 2 minutes until fragrant and golden.

Pour 1.75 cups beef broth, 2 tbsp Worcestershire sauce, and 1 tbsp tomato paste into the skillet, stirring to scrape up all the flavorful browned bits from the bottom.

Pour the warm skillet liquid over the roast, then arrange 1 lb carrots, 1.5 lb halved baby potatoes, 2 rosemary sprigs, and 3 thyme sprigs around the beef, sprinkling the remaining 0.5 tsp salt and 0.5 tsp pepper over the top.

Cover and cook on Low for 8 to 9 hours (or High for 4 to 5 hours) until the beef is melt-in-your-mouth tender.

Transfer the roast and cooked vegetables onto a warm serving platter, discard the herb sprigs, and cover loosely with foil.

Whisk 2 tbsp cornstarch with 2 tbsp cold water, then stir the mixture along with the remaining 0.25 cup beef broth into the slow cooker liquid, cooking on High for 15 minutes until thickened into a rich gravy to serve over the roast.