I first learned of this brilliant
cult genre through multimedia wunderkind
Logan Whitehurst, but it may well be a widespread and venerable
school of art among
copy centre employees - flourishing among its handful of adherents away from the withering gaze of public awareness.
In short, copier art is essentially the creation of collages but with a notable restriction; the sources from whence you are permitted to procure visual samples of images and text are restricted to the garbage bins of your workplace. (Intentionally seeding the workplace trash with visually-interesting litter is not permitted.)
Having obtained images to alter and rearrange, you then assemble the final piece of collage surreptitiously utilizing only those tools which are regularly present at your workplace already. Although elementary schools are no doubt replete with the glue and scissors which are the lifeblood of collage work, this further restriction makes apparent the genre's intractable geographical association with copy centres - production of copier art would certainly be more difficult in different work environments (to say nothing of the qualities of the visual samples available) but perhaps there are some who would appreciate taking on the extra challenge of producing copier art in more hostile-to-creativity environments.
Elements assembled and arranged, a single photocopy is made of the final work, after which its constituent components are returned to the garbage what begat them. (Otherwise that's STEALING!) Take it home, give it to a friend as a gift, send it through the mail or post it up somewhere where the producer of its sampled trash might see it.