Over at How to be a children’s book illustrator, they’ve got some video of Brian Selznick explaining his creative process.

The key idea to take away is this: creating a successful picture book requires having a vision for the entire project.  You can’t think in terms of  ‘one illustration at a time.’

Brian accomplishes that by making a little dummy—a cut-and-pasted version of the book made out of his sketches—so he can see the entire book while he’s still creating it.