Preheat the slow cooker on a high setting
Season the beef with salt and pepper
Place into a skillet and let it brown for 4-6 minutes
Take it out and leave it to one side
Add in the onions to the same skillet and cook for 3 minutes stirring gently
Now to the slow cooker add the carrots, potatoes, broth, bay leaf, thyme, tomato paste, garlic, and Worcestershire sauce
Cut the beef into chunks and place back into the slow cooker
Give everything a good mix and cook on low for 7 hours
In a separate bowl combine the butter and flour and add to the stew
Cook for another hour