Josh Boone is attached to direct the film based on Stephen King's epic, post-apocalyptic bestseller. The filmmaker, who is already attached to the King adaptation Lisey's Story, will likely write (or at least take an active hand in it) as well as directing; previously, writer/director Scott Cooper was attached. Before him, it was Ben Affleck and before that, David Yates.
Yates left, saying that there was no way to do it justice as a stand-alone film and that it ought to be a TV miniseries--which it already was, in 1994. Affleck left because the project would be too large for him to take on while playing Batman in a series of DC Universe movies, also for Warner. The Best Picture winner will presumably be directing some smaller projects along the way anyway, but as Batman vs. Superman took shape, Affleck became briefly attached and then dropped out of a couple of projects.
The role of Flagg was played by Law & Order: Criminal Intent veteran Jamey Sheridan in a 1994 TV miniseries based on the novel. Sheridan has appeared in Arrow as Oliver's father Robert Queen.
The Stand is full of religious imagery, and Flagg is widely understood to be the devil, or at least a very powerful demon. He touches off the plague that the story centers around and elevates himself and those close to him to positions of power in a new mob-rule as governments begin to collapse.
There is no official release date and no one has yet been cast for the film, which has been in and out of development for several years.