I did a bit of looking on line, I'm thinking that back page was an advertisement page for the magazine and products?
Without having seen the picture ourselves, it's really super hard to figure out among the many "flower power" projects out there it could be. But some of our members do have the digital or physical copies and may be able to look it up.
When you do a google on "fons and porter flower power kit" there is one actual kit being sold on ebay. That is not the pattern you are searching for?