Heat the oil in a large pan over medium-high heat, add the beef and brown on all sides, about 20 minutes and set aside. Add the onions and cook until tender, about 2-3 minutes, before adding the garlic and red pepper flakes and cooking until fragrant, about 1 minute.
Place the beef, onions, broth, balsamic vinegar, soy sauce, brown sugar, Worcestershire, carrots, and potatoes in a slow cooker, cover and cook on low for 8-10 hours or on high for 3-5 hours.
Remove the carrots, potatoes, and beef and slice or shred the beef. Skim any fat from the cooking juices, place it in a saucepan, bring to a simmer, add the cornstarch/water mixture and cook until the glaze has thickened a bit. Serve with the beef. Enjoy!