The origin of Fabrizio Salani's "AG" monagram

[Fabrizio Salani]

So if I understand correctly, the wax wasn't applied directly to the parchment, but rather a cardboard material in between. Is the glue between the wax and the cardboard, or is the glue between the cardboard and the parchment? 

I don't understand why glue would be required to stamp a seal onto parchment. Is the idea that a piece of cardboard was glued to the parchment, and then hot wax was carefully poured onto that cutout, and then the imprint made? Perhaps that is normal, I don't know. 

Or perhaps a cutout from somewhere else attached to the parchment makes sense, like an old wax seal collection: 

This is the right sequence: treated parchment, glue, cardboard, seal.