Here's a couple that I created:
It was so fun making these! And you REALLY have to think through the problem step by step to make sure you show ALL your thinking in the GIF - I love thinking of the students having to go through that kind of thought process when making these!
I started by creating the images using Google Slides. You just make your first slide that shows the problem, then duplicate the slide and show the first step. You keep duplicating the slide and then making a change until you get to the end of the problem. Then you download each slide as a jpeg. I used gifmaker.me to create my GIFs - you just upload your jpegs in the order you want to them to appear in the GIF. I set the animation speed on both of these to 1000 and then you just click the big "Create GIF Animation" button on the right hand side of the page. Once the GIF is created, you'll see a link that says "Download GIF". Voila! I cannot wait to use this as an assessment tool next year!