A photograph here from Ed Williams taken on our Flash Photography Workshop.
The sun has many important things to do with daily life, none more important than standing in as a hair light when you only want to use one flash.
Simply put, we placed the model with her back to the sun, and then fired a flash (off camera) through a diffuser as the main light. This has created a nice soft light for the face, and we have a lovely bit of light in the hair from the sun.