Here are two more fascinating YouTube videos exploring the relationships between national flags. Their creator goes only by the name Vexillographer.
“Transforming Transnational Flags” by Vexillographer, published 11 March 2012. 30 national flags. Produced in Microsoft PowerPoint.
“Construction Paper World Flags” by Vexillographer, published 16 February 2015. 22 national flags. A mistake: “You might notice a failed attempt at Gabon’s flag near the end, which I messed up by getting the order of the colors wrong. Oops.”
BTW, construction paper cutouts are an excellent medium for prototyping flag designs. Unlike pen and paper, or pointer and software, they resist attempts at over-complicated designs. Doug Lynch, designer of the Portland flag, was a strong proponent of this.
Portland Flag Association 
what is this?