Season the chuck roast generously with salt, pepper, and thyme. If desired, sear the roast in a hot pan for a few minutes on each side to create a brown crust.

Slice the onion and mince the garlic. In the slow cooker, layer the sliced onions and minced garlic at the bottom. Add the whole or cut potatoes and carrots on top.

Place the seasoned roast on top of the vegetables. Pour in the beef broth and add any optional ingredients like Worcestershire sauce or red wine for additional flavor.

Cover the slow cooker and set it to cook on low for 8-10 hours or on high for 5-6 hours, being careful not to open the lid during cooking.

Once the cooking time is complete, check the roast for tenderness. If desired, whisk together cornstarch and water, and stir it into the slow cooker to thicken the gravy. Shred the roast and serve it with the vegetables and gravy.