Hi Gina,
We cut small tags with qr codes at Maker Faire out of engraving plastic. We generally cut a bunch of blank tags beforehand and then use this holding jig with a recess to keep them in place while cutting. It works really well, is quick to insert and remove the blanks, and keeps everything registered correctly for cutting.
The large recess at the bottom is just a finger hole to make it easier to remove the cut tags, and the two ramping grooves on the sides are to attach thin strips of wood or plexiglass to press down on the edges if you need extra hold...we rarely use them unless we're using an up-spiral bit that wants to lift the tags.
Bill