To structure an essay using flashback subtitles, organize your narrative by creating clear, thematic headings that mark shifts between past and present, helping to guide the reader through complex timelines. For a narrative, consider using headings like "Ten Years Earlier: The Catalyst" or "Present Day: The Aftermath" to signal the shift [BBC Bitesize, Good Story Company]. In academic writing, subheadings, such as "Historical Context," act as signposts to guide the reader through the structure, rather than just acting as a label [Goldsmiths University].