Decoupage is a paper glue crafts technique done by gluing and layering paper cutouts on a canvas, frame, box or other object until the desired look and design effect is achieved. The eventual design depends on the types of printed papers or shapes you're using. Once the layering effect is finished, you can apply a protective decoupage sealer glue such as Aleene's decoupage glue or varnish over the top to protect and seal the paper layers.