Rub both sides of the meat with salt. Drizzle a large pan with olive oil over high heat and sear each side of the chuck roast for about 3 minutes to get a nice crust.
Place the chuck roast in a slow cooker or dutch oven.
Saute the onions with garlic powder in the drippings over medium-high heat in the same large pan that you seared the meat in. After two minutes, add the balsamic vinegar. Let simmer and stir frequently until it becomes syrupy.
Turn heat off and stir in the Dijon mustard. Add this balsamic Dijon mixture in with the meat. Throw in the thyme sprigs, baby potatoes, whole carrots, salt, pepper, and the beef broth.
Cover and let it cook on low for 8 hours in a slow cooker. Or about 3 hours on 300 F degrees in the oven.