Our friend Paula posted a video showing how to fold a small square out of paper. I thought it would be fun to ask my younger son to fold a small square before watching Paula’s video to see how he’d do it. Here’s what he did:
Next I asked him to watch Paula’s video:
Now I asked him to recreate Paula’s technique and talk through why it worked:
Mike's Math Page 
I LOVE the method that your son came up with! I’ll play dueling paperfolding with you all anytime! (ps what I like about both these methods is that you can see a line that can be thought of as a y = x equation, thus making it easy to scale the squares. Mine show the line via the fold, but his can easily be drawn, connecting the corner edge to the point where his folds intersect.)