Hi, I'm Sue Walker and I'm going to show you how to thicken stew in a slow cooker. The things you will need are, your hot stew, some mashed potato flakes, or some cornstarch, a one tablespoon measuring spoon, and a whisk. The easiest way to thicken stew in a slow cooker is to use instant mashed potato flakes. You just add the flakes directly to the stew and stir until they dissolve. Add enough flakes until the gravy thickens to the desired consistency. Another way is to use cornstarch and water. This is better than flour because you can won't get the lumps or the flour taste. Add two tablespoons of cornstarch to one cup of water and mix until smooth. Add it gradually to the stew while stirring. Keep adding until you get the right thickness. And that is how to thicken stew in a slow cooker.