Season the roast: Pat the chuck roast dry with paper towels and season all sides generously with salt and black pepper.
Sear for flavor: Heat olive oil in a skillet over medium-high heat and sear the roast for 2-3 minutes per side until a deep brown crust forms. This step builds the base flavor for the gravy.
Layer the vegetables: Place the potatoes, carrots, and onion in the bottom of the crock pot. This lets the roast sit on top and baste the vegetables as it cooks.
Add the roast: Set the seared roast on top of the vegetables in the crock pot.
Mix the braising liquid: Whisk together the beef broth, tomato paste, soy sauce, rice vinegar, garlic, thyme, and rosemary in a bowl until combined.
Pour over the roast: Pour the liquid mixture over the roast and vegetables, making sure it reaches partway up the sides of the roast.
Cook low and slow: Cover and cook on low for 8 hours, or until the meat shreds easily with two forks. Avoid lifting the lid often, since this lets heat escape and slows cooking.
Remove roast and vegetables: Carefully lift the roast and vegetables onto a serving platter, leaving the liquid in the crock pot.
Thicken the gravy: Whisk the cornstarch and cold water together in a small bowl, then stir this slurry into the hot liquid in the crock pot.
Simmer until thick: Set the crock pot to high and let the gravy simmer uncovered for 10-15 minutes, stirring occasionally, until it thickens and turns glossy.
Shred and serve: Break the roast into large pieces with two forks, then pour the warm gravy over the meat and vegetables before serving.