According to a report by THR the director and screenwriter for the upcoming DC Comics adaptation The Flash is Seth Grahame-Smith. Barry Allen will be played by Ezra Miller.
The film follows the DC movie universe that started with Man of Steel and will be taking place after Batman V Superman and Justice League part 1. We will get to see Ezra Miller’s role as Flash in Justice League part 1 in November 2017 before his solo film in March 2018.
This movie will have no connection to The Flash television series on The CW. The universe of the television shows The Flash, Arrow, and upcoming Legends of Tomorrow are part of a separate DC universe than the upcoming films of Batman V Superman, Wonder Woman, and The Flash.
Grahame-Smith is known for writing screenplays like Abraham Lincoln: Vampire Slayer and the upcoming LEGO Batman the movie for Warner Bros.