Season both sides of the chuck roast generously with kosher salt and freshly ground black pepper.
Heat the olive oil in a large skillet over medium-high heat.
Place the chuck roast in the hot skillet.
Sear the roast on both sides until well browned.
Remove the roast from the skillet and transfer it to the slow cooker.
Add the quartered onions to the same skillet.
Cook the onions over medium heat until they are browned around the edges.
Reduce the heat to low.
Add the coarsely chopped garlic to the skillet.
Cook for 1 minute, stirring frequently to prevent the garlic from burning.
Transfer the browned onions and garlic to the slow cooker with the chuck roast.
Add the beef broth, dry red wine if using, Worcestershire sauce, chopped rosemary, chopped thyme, and bay leaves to the slow cooker.
Cover the slow cooker with the lid.
Cook on HIGH for 2 hours.
Add the carrot chunks and baby yellow potatoes to the slow cooker.
Cover again and continue cooking on HIGH for an additional 2 to 3 hours, or until the roast is tender and the vegetables are fully cooked.
Carefully remove the chuck roast and vegetables from the slow cooker.
Place the roast and vegetables on a cutting board or serving platter.
Cover loosely with aluminum foil to keep warm.
In a small bowl, whisk the cornstarch and water together until smooth.
Slowly whisk the cornstarch mixture into the liquid remaining in the slow cooker.
Cover the slow cooker and cook on HIGH for 10 minutes, or until the gravy has thickened.
Remove and discard the bay leaves.
Slice the chuck roast against the grain.
Serve the sliced roast with the carrots, potatoes, onions, and prepared gravy.