Season the beef with salt and pepper. Heat the oil in a large skillet over medium high heat. Sear the beef (you will probably need to work in batches) on all sides then transfer to the slow cooker.
Add the onions, celery and garlic to the pan and saute until they begin to soften. Stir in the tomato paste and cook for another minute. Pour in the wine and scrape up any browned bits on the bottom. Transfer the mixture to the slow cooker. Stir the cornstarch into the beef broth and add that to the slow cooker as well as the Worcestershire sauce, thyme, rosemary and bay leaves.
Wrap the chopped potatoes and carrots in a foil packet and nestle that on top of the stew. Cover and cook on LOW for 8-10 hours or HIGH for 6-8 hours. Serve and enjoy!