WHAT EXACTLY IS "COLOR FLATTING"?
Over the years I've certainly flatted thousands of pages of comics, and, while it's been a standard practice in comic making for many decades, I've found most people don't fully understand the process or its purpose.
Simply put, flatting is the first step in the coloring process. After receiving inked pages, a flatter lays down flat coloring that is layered underneath the line art. The color layer(s) create "trapping" underneath the inks, to help compensate for alignment issues in offset printing. This helps prevent gaps between line art and color.
To the left is the flats layer for the season six trade paperback front cover art of Zander Cannon's Kaijumax, a series I've flatted for nearly its entire run. See more examples below from other projects I've flatted!
Kaijumax © copyright Zander Cannon.