You can piece them or applique them. There are numerous patterns out there for pieced blocks. I know the book The Cats Meow by Janet Klime has instructions as well as numerous wonderful cat block patterns.
https://www.amazon.com/Cats-Meow-Pur...=the+cats+meow
Here is a blog I found that has downloadable patterns for the alphabet as well. She mentions numbers 1-9 but I didn't see a link for those.
https://fabricfrantic.myshopify.com/...block-patterns
And as Artsy one suggested you can certainly graph your own with graph paper. The beauty of that is you can make them any size you want and aren't limited to already made patterns.