Insert the words "FLASHBACK TO:" in all caps and right-align it on your screen play document. If using screen writing software, this task may be simpler than if using normal word processing software.
On the next line, write the slug line just as you would for a normal scene with a year for date following in parenthesis. A slug line is the short descriptor that tells the reader where the scene is taking place and at what time of day. An example of a slug line is as follows: "INT - MORRISON'S LIBRARY - DAY (1996)." The slug line should show first whether the scene is inside (INT) or outside (EXT). It should also include the precise location of the scene, in this case Morrison's library, and what time of day it is during that scene, in this case, day.
Insert the flashback dialogue. Treat the dialogue as if it was in a steady, chronological plot stream. On the next line, place the character's name in all caps in the center of the page. On the line following that, center the character's speaking lines. If another character speaks, start another line with that character's name in all caps in the center of the page, followed by his or her words on the next line, and so on.
Return to the present by inserting, in all caps, the words "BACK TO PRESENT" on the far right of the page.