Creating Crockpot Garlic Beef is straightforward if you follow these simple steps:

1. Prepare the Beef: Trim any excess fat from the beef chuck roast and cut it into large chunks.
2. Sear the Beef: In a large skillet, heat the olive oil over medium-high heat. Sear the beef chunks on all sides until browned (about 3-4 minutes per side).
3. Add Ingredients to Crockpot: Place the sliced onion, minced garlic, and seared beef into the crockpot.
4. Mix the Sauce: In a separate bowl, whisk together the beef broth, soy sauce, Worcestershire sauce, brown sugar, thyme, black pepper, and salt.
5. Combine: Pour the sauce mixture over the beef and onions in the crockpot, ensuring everything is well coated.
6. Cook: Cover the crockpot and cook on low for 8 hours or on high for 4 hours, until the beef is tender and shreds easily.
7. Optional Thickening: If you prefer a thicker sauce, mix the cornstarch with 2 tablespoons of water to create a slurry. Stir this into the crockpot during the last 30 minutes of cooking.
8. Serve: Once cooked, shred the beef using two forks and mix it back into the sauce. Adjust seasoning if needed.

These steps will guide you in creating this incredible dish effortlessly.