Optical Illusion How-to Video - grade 5 and 6

First of all, a big hello to my new followers! Thanks to some much appreciated support from a fellow art blogger, I've gotten quite a few new followers in the past day. Thanks to everyone for your continued support! Now onto my post...

There's an optical illusion that's been all over the art blogs for a while now, which I believe originated here. I have always wanted to try it, but couldn't quite figure it out, even when looking various types of instructions. I showed it to my students, and some of them just got it. They were blowing me away with how easily they it out, and how fluidly they could make the illusion work. I asked one of my lovely girls to do another copy of her art work, so that I could film her and upload it. Hopefully this will help anyone who is having trouble figuring out this amazing illusion!

Here's one in progress:

and here's her finished work:

I'll post more as they are finished!