Pat the chuck roast dry and season all sides with salt and pepper
Heat oil in a skillet over medium-high heat
Sear the roast on all sides until browned
Place sliced onions, carrots, and potatoes in the slow cooker
Add minced garlic if desired
Place the seared roast on top of the vegetables
Pour in beef broth
Add Worcestershire sauce, tomato paste, and herbs such as thyme and rosemary
Cover and cook on low for 8 to 10 hours or on high for 4 to 6 hours
Check that the roast is tender and shreds easily with a fork
Remove the roast and vegetables from the slow cooker
Skim excess fat from the cooking liquid if needed
Mix cornstarch with cold water and stir into the liquid to thicken the gravy
Return the roast and vegetables to the slow cooker or serve with gravy on top
Slice or shred the roast and serve warm