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
Alphabet Play Dough Mats and many more letter ideas. Have kiddos start out by finger tracing a letter, then using a dry-erase marker and then building the letter using small objects. Practice makes perfect!