Check out this amazing resource: Debbie Ohi's Free Picture Book Thumbnail Templates for Writers and Illustrators
The 32 thumbnails is very useful (and arguably better than folding a piece of paper into 32 rectangles,
but it's Debbie's Reference Layout that feels innovative—especially for illustrators, with Debbie giving you space to sketch options for each spread!
She even shares the above example of how she uses the template.
It's a great and generous public service to her fellow writers and illustrators—you'll find these picture book thumbnail template resources that you can download yourself here.
Illustrate and Write On,