These use of multiple z's which is often placed with the idea of sleeping, help emphasize the word Lazy. Even though lazy isn't spelled with multiple Z's the reader can figure out what the word is due to the subscript z's.
Had when i worked in a preschool and kids love them! I would use colored sand instead of white salt. DIY salt tray with alphabet cards. Easy to make and kids have fun smoothing out the salt after correctly making the letter