To make this delicious broccoli cheddar soup gluten-free you can easily replace the all-purpose flour with a gluten-free flour blend. You can find gluten-free flour blends in stores that work just as well as regular flour. Alternatively, you can use cornstarch as a thickening agent, for those avoiding gluten. To do this simply mix 4 tablespoons of cornstarch with a small amount of water to create a slurry. Then add the slurry to the soup during the simmering step to achieve your desired thickness. This simple substitution allows individuals, with gluten sensitivities to savor the flavorful goodness of broccoli cheddar soup worry-free.