Roll up the newspaper lengthwise. Roll the paper tightly and put masking tape around the middle to secure it.
Place the middle of the rolled up newspaper over a rubber band with both sides of the band visible on either side of the newspaper cylinder. The band should be short enough that it has to be stretched to reach around the newspaper.
Take both ends of the rubber band and pull them around the newspaper. Thread one end of the rubber band through the other end where they meet and hold onto this part of the band to keep it in place.
Push the bottom end of the spoon through the part of the band that you are still holding and release it so that the base of the spoon is held in place against the newspaper. The bowl of the spoon should be facing upward.
Place the newspaper on a table so that the plastic spoon can be bent well backward and when it is released it springs up with some force.
Secure both ends of the newspaper to the table with masking tape.
Fire your marshmallows or rolled-up pieces of paper from the bowl of the spoon, pulling the spoon back before each shot.