Add the chicken broth to a saucepan on medium-high heat. Bring to a boil.
In a separate bowl, combine the flour, milk, and seasonings. Stir until the flour is completely dissolved.
Slowly add the milk and flour mixture to the boiling broth, stirring continuously.
Reduce the heat to medium-low and continue cooking, stirring frequently, until the soup thickens (about 6-10 minutes).
Allow the soup to cool fully before serving.