There are a dozen different recipes and ideas for moon sand out there. This one is a favorite because it includes ingredients you either have laying around or can get easily, even if you live in the middle of nowhere. The link below gives a little story, fun pictures, ideas, and detailed instructions. However, the idea is simple:
8 cups plain flour
1 cup baby oil (or any oil if you’re concerned with using baby oil)
Mix and play! It is great for ages 2+ and is messy but easily cleaned.