Welcome to THO.
Soundboards are placed insided the call, underneath the playing surface. You can make them from wood, acrylic, glass, various metals and slate. Glass is a good starter material and will work with any playing surface. Aluminum is a great sounboard. Slate can be a little delicate as a soundboard if the call is dropped, as it can easily shear off the pedestal. Soundboards should be placed no more than 1/8" under the underside of the playing surface. Use plumber's Goop to adhere your soundboards and surfaces.
Every question you couple possibly think of has been asked and answered in this forum, so get comfy and start reading through previous threads, use the search feature and read all the tutorials. If you have any question don't hesitate to ask.
