I start with a small image of one of my paintings, apply a glob of glue, then squish the gem into the glob and slide it around until the glue is evenly distributed and the image is centered. The photo shows what it looks like at this stage.
After the glue has had time to cure, I’ll trim the edges, glue on the pin back, and then seal the back and edges with a mat varnish.
Alternatively, I could glue a magnet on the back, in which case I’d skip the varnish.
*silcone-based industrial-strength adhesive