Small sand waves don't appear

You're really close! It looks like you followed my approach very accurately. The voronoi and mapping nodes have changed since this video was recorded, so that's likely causing a difference in the result.

You clearly have a small, secondary 'wavy' pattern involved but it doesn't read like an obvious voronoi derivative the way mine does. It's hard too tell what's different just by looking at the node network.

If you're willing to post a download link to your .blend file, I'd be happy to take a closer look at what's going on. The best way to do this is by uploading to Dropbox, Google Drive, or equivalent file hosting service then copy and paste the share download link here.

Thanks for providing your .blend file. Turns out to be a simple fix! The voronoi texture at the bottom is using the Color output instead of the Distance output:

 Using the distance produces the expected results.