Optional: Sear the chuck roast in olive oil on all sides in a hot skillet.
Place sliced onions and chopped carrots in the bottom of the crock pot.
Lay the chuck roast on top of the vegetables.
Pour in beef broth, Worcestershire sauce, and tomato paste (if using) around the meat.
Sprinkle the roast evenly with salt, pepper, garlic powder, onion powder, and thyme.
Cover and cook on LOW for 8–10 hours or HIGH for 4–6 hours, until fork-tender.
Optional: Remove roast and whisk in a cornstarch slurry (1 tbsp cornstarch + 2 tbsp water) into the juices to thicken.
Shred roast and serve with pan juices and sides of your choice.