Melt butter in a large saucepan over medium-low heat. Add flour; cook 3 minutes, stirring. Whisk in broth.
Increase heat to medium-high; bring mixture to a boil, stirring constantly. Reduce heat to low; let simmer 15 minutes, stirring. Let cool completely. Transfer to container, cover, and refrigerate up to 3 days.
When ready to serve, reheat gravy, add pan juices from turkey, and heat to boiling. Thin gravy with more broth or water if it's too thick.