Generously season the beef with salt and pepper, then slice the onion and garlic
Sear the beef in oil over a medium-high heat on all sides
Add the meat to a slow cooker and add onions to the pan along with red wine. Once the onions have softened slightly, add the garlic and carrots
Transfer the vegetables to your slow cooker along with tomato paste, balsamic vinegar, soy sauce, Worcestershire sauce, beef bouillon, fresh thyme, fresh rosemary and bay leaves. Add water or stock to cover ¾ of the meat
Cook for 6-8 hours, then place the roast in a pan. Ladle the vegetables from the slow cooker on top. Roast at 400ºF/200ºC for 20 minutes
Pour the sauce from the slow cooker into a pot, then add a thickener. Whisk until combined and thickened, then add butter and whisk again. Cover the beef and allow to rest for 5 minutes, then serve with the gravy and enjoy!