Saturate cotton balls with water and place in the bottom of the plastic container. Add a few drops of nail polish remover, which will prevent fungus from developing.
Cut a piece of cardboard large enough for the moth to rest upon. Place the cardboard over the cotton balls to provide a barrier for the moth.
Pick up the moth with forceps and place the moth on top of the cardboard. Keep the moth in the container for three days.
Remove the moth from the container and lay it flat on the spreading board. Let the moth's wings dry, which can take up to a week.
Place the moth on the pinning block. Gently place a pin through the moth's thorax and push the pin through the pinning block.