This is a super quick and functional sewing project. It took me all of 20 minutes and they actually managed to stay on my child even though her primary form of transport right now is the army crawl. I got my inspiration from here and then gathered:
Long women's socks (I already had tons to choose from)
Scissors Elastic thread and needle (or sewing machine)
You basically cut off the heel and toe of each sock. Fold your smaller piece in half, fit it over the bigger piece and sew with your elastic thread. You are sewing three layers together as you can see in the figure below. Really not hard.
Here's Lily in her new socks, she thought they were pretty legit, even giving them a thumbs up.