Use a tray filled with salt for tracing practice.
By tracing in the salt* with a pencil eraser, the child can compare his or her letter (or number) to the one shown on the card. It's easy to repeat over and over, and if kept in a tray deep enough, should be mess-free**.*Not for the superstitious teacher, though.**Yeah, kids are messy and never listen so this could end up being messy.