Clear soups are tasty, but if you want a thicker, heartier soup, you don't have to add flour or cornflour -- you can blend part of the soup to thicken the rest of it. An immersion blender works best. If you don't have one, you can also use a potato masher or standing blender.
Image from neeta_lind
As Christine Gallary, writing on The Kitchn, points out, this technique thickens the soup without changing the flavour the way that a slurry -- the opposite of a roux -- would. She also warns that if your soup has bones, you should remove them before you blend. For more tips on this method, check out the full post linked below.
The Easiest Way to Thicken a Soup [The Kitchn]