Creating the incredible dish of Slow Cooker Beef Manhattan is straightforward if you follow these simple steps:

1. Prepare the Beef: Trim any excess fat from the chuck roast and cut it into big chunks for even cooking.
2. Sear the Beef: In a large skillet, heat olive oil over medium-high heat. Sear the beef chunks for 2–3 minutes on each side until browned.
3. Add Ingredients to Slow Cooker: Transfer the seared beef to your slow cooker. Add diced onion, minced garlic, beef broth, Worcestershire sauce, thyme, salt, and pepper.
4. Combine Well: Stir the ingredients gently to ensure the beef is coated in the broth.
5. Set Slow Cooker: Cover your slow cooker with its lid and set it to low for 8 hours or high for 4 hours.
6. Check Tenderness: Once the time is up, check that the beef is fork-tender. If it isn’t tender enough, let it cook for an additional hour.
7. Thicken the Gravy (Optional): If you prefer a thicker sauce, mix cornstarch with a little cold water to create a slurry. Stir this mixture into the gravy and let it cook for an additional 30 minutes.
8. Prepare for Serving: While the beef is finishing, toast slices of bread or prepare mashed potatoes.
9. Serve: Spoon the beef and gravy over the toasted bread or mashed potatoes. Garnish with fresh parsley if desired.

These straightforward steps will guide you in preparing the Slow Cooker Beef Manhattan seamlessly.