The first few times you fold up the Oru Kayak it will be more difficult than it looks in the instructional video. This is because the material is not very flexible yet. It will become more malleable over time and easier to assemble and fold back into the box. I recommend kneeling or sitting on the kayak to get it back into the box. The following video demonstrates how to do this.
Here is a link to the Official Oru Kayak Assembly Video (starting at folding it up).