"Thinking outside the box" is to understand creative thinking. This means that you should have system or process for driving your creativity. The author listed a four step process for creativity. 

Three ways to think outside the box include: preparation- setting the ground work for the thing you want to create by gathering information, incubation- this is the process of organizing the the information gathered in the preparation stage, illumination- this is the process of the "ah ha" moment resides and it comes after you have sifted through all of your information thus far, and finally verification- where you are able to confirm either through analysis or others analysis that you have created what you set out to create.