I'm not sure specifically as I haven't read a 'flake graphic novel' myself. It could be about all sorts of things. Maybe it's about a character named Flake and their adventures, or it could be a story set in a world where snowflakes have some sort of special significance and the graphic novel explores that in a visual and narrative way.
A 'flake graphic novel' might deal with themes that are unique and somewhat off - beat. It could be a story that plays with the idea of being 'flakey' in a humorous way. For example, the main character could be a person who is constantly changing their mind or doing things in an unpredictable manner, and the graphic novel could use its visual format to really bring out the comical aspects of this flakey behavior. The art style might be really quirky to match the theme too.