Soldering to the piezos:  The Piezos are a brass disc with a crystal on one side,  the brass is the '-' and the white part, the crystal is the '+'.  You can buy them with the wires already soldered in place or you can do it yourself.   

You should use a thin flexible wire.  Soldering is pretty strait forward but caution should be used when soldering to the crystal,  I used pretty low heat, 250deg C.   Hotter temps can damage it.  For the brass part turn your heat up because it is such a heat sink,  I use 350deg C for the brass.

Laser cut 4 sets of Piezo Mount.SVG out of any non conductive ~.25" material.  

These get stacked up and glued together,  I used acrylic and Rez-N-Bond.

Next feed the leads thru the holes and solder on the screw terminal.

Super glue the terminal black down.

Cut a 1.5" circle from 1" thick polyurethane foam and cut a slit in it for the wires.  

Place the foam in the housing and the piezo on the foam.

Add the 3M Command Strips.

Make 4