Pat the beef chuck roast dry with paper towels and season all sides with salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat. Sear the roast on all sides until browned, about 3-4 minutes per side. Remove from heat.
Place the sliced onion and minced garlic in the bottom of the crockpot.
Place the seared roast on top of the onions and garlic.
Add the beef broth, red wine, fresh thyme, fresh rosemary, bay leaf, and Worcestershire sauce to the crockpot.
Cover and cook on low for 8 hours, or until the beef is tender and easily shredded with a fork.
Remove the roast from the crockpot and cover with foil to keep warm.
Strain the cooking liquid into a saucepan and discard the solids.
Bring the cooking liquid to a simmer over medium heat.
In a small bowl, mix the cornstarch with cold water until smooth to make a slurry.
Slowly whisk the cornstarch slurry into the simmering cooking liquid and cook for 2-3 minutes until the au jus thickens slightly.
Serve the beef roast sliced with the au jus poured over the top.