Start with a character
- - Who are they? (age, gender, ethnicity, species, etc.)
  - What are they? (occupation, role in family/community/society etc.)
What do they want?
Why can’t they get it?
What do they try to do to get it?
- - This is called the inciting incident.
Does it work?
- - Most stories have a TRY/FAIL cycle where the characters try to reach their desire or the resolution of the plot, and fail in different ways. This can also be described as the YES, BUT. . . / NO, AND. . . formula. It’s similar to the theatre improvisation principle of always saying “yes, and. . .” to your acting partner to keep the action moving forward.
  - YES, BUT: The thing the character tries works (yay!), but something else goes horribly wrong. This is a one step forward ("yes" moves you closer to the goal), two steps back situation ("but" moves you further away). For example, if the character wants to get to a castle on the top of a mountain, she might try to build a hot air balloon to fly up. Does it work? YES, she successfully builds a balloon, BUT the wind blows down from the mountain peaks and carries her and her balloon far away.
  - NO, AND: The thing the character tries fails, and something else goes wrong. If we take the same story from before, the character might try to lasso a treetop to stop the balloon. Does it work? NO, AND in the attempt, she falls out of the basket and gets tangled in the ropes hanging from the balloon. Very perilous! NO, AND increases tension because rather than being forward and then backward progress, it is just backward progress taking the character further away from their goal.
  - Repeat the cycle as desired until you have a story.
How do they resolve their desire?
- - Here you take the YES, BUT/NO, AND formula from above, and instead of having everything go wrong, you reverse things to YES, AND/NO, BUT to make things go right!
  - This is where you ask yourself if the thing the character wants is what they ultimately need. This is an existential/emotional need such as acceptance, self-confidence, forgiveness, purpose, etc.; it isn’t a material need like food or shelter. You can either resolve your story by having them achieve their desire, or discover something even better (such as the infamous, “Maybe the real treasure was the friends we made along the way” trope). If you are writing a longer story, you can add tension by making the desire and need conflict with each other.

Keep in mind, you are writing a six page book. You do not have much space to tell a story in! Do not use this as the opportunity to cram the entire epic fantasy webcomic series you've been dreaming about writing since high school into six pages. You will be frustrated, and the result will not capture what you want it to. Pop-up books are typically between 6-8 pages, maximum. You want to have fully introduced the character and conflict in the first two spreads, fit one or two try fail cycles into the third and fourth spread (possibly the fifth spread depending on how concise you make the ending), and resolved everything in the sixth.

Here is a really excellent video about structuring stories (specifically short stories, but it applies to all narratives) by Mary Robinette Kowal. The video itself is forty-five minutes long, but you can watch just the first eleven minutes for a concise, thorough powerpoint on story structure.