The curtain is finally pulled back on the next chapter of DC storytelling. Gunn revealed that The Flash was going to do a reset, yet existing characters and superheroes already being around may indicate this is not a full reset. This begs the question whether or not the viewer is going to be confused and doesn't know what is going on in this new universe.
One of the announced projects is an animated show starring The Suicide Squad's Weasel and a new team formed by Waller called the Creature Commandos. This will be the first project in Chapter 1 of the DCU, and together with the live-action show starring Viola Davis as Waller herself can function as the introduction to this post-Flash reset universe.
Introduction through context
One of Gunn's previous endeavours in the DC universe, The Suicide Squad, already shows Gunn's ability to work inside an already populated universe (1). The first ten minutes follows Savant from Belle Reve to his death. Savant, and thus the viewer, is introduced to Task Force X, learning that it has been operating for some time, what the goal is, who it employs and who runs it, and show that superpowered people inhabit this world.
This introduction through a point-of-view character, where everything is introduced in context of his/her perspective, the viewer quickly learns about the what, the who, and the why. Other projects that employ this technique as well are A New Hope through the droids (2), The Last of Us episode 1 through Sarah, EEAAO through Evelyn, Lord of the Rings through Frodo, and Gunn's own Guardians of the Galaxy through Star-Lord. The Leftovers episode 1 does introduce more POV characters, but quickly ties it to Kevin.
Everything is done within the context of the character's stories and decisions. It rarely cuts away suddenly, never to give away information much earlier to the viewers than to the main characters. When it does, it is relevant to or logically follows from an in-narrative situation, or is interlaced with it (3). There is still room for POVs, like the villain's, to be shifted or added, and for hints that inform of larger worlds to be dropped too, like Fury in Iron Man, or a picture of Batman in Man of Tomorrow without it feeling out of place.
Introduction to the DCU
What The Suicide Squad and others show is that the viewer can quickly accept the status quo of already developed universes, even if certain threads happened off-screen. With Gunn's movies, the viewer is not introduced to ongoing threads until the movie wants the POV character(s), and thus the audience, to know about them without it feeling forced. And like The Expanse shows, everything that is introduced makes sense to it's wider universe, whether it's fictional or not (4).
That is exactly what Creature Commandos and Waller can do: introduce the viewer to the wider DCU within the context of it's own story through characters relations and situations without turning into exposition dumps. That way the viewer rapidly catches on with the what, the who and the why of that world, and build from there. Like Gunn did with The Suicide Squad and Peacemaker: one sets the world up, the other naturally progresses it.
Waller especially can serve as a set-up to explain what and who is around. Who that will be remains to be seen though, as some characters will appear in movies this year and nothing concrete might be decided before their release. Batman and Superman however will get a fresh start, as the focus appears to shift to long-term storytelling current incarnations don't fit.