First we make a large sheet of firm material. In our example we use a piece of melamine just because it will tend to be a little more durable overtime. We make "plates" on the front so that we can make them for different sizes of speakers. You don't have to go to those lengths for basic testing, just cut a hole that is
required by the speaker and install.
The board has to be large enough to separate the sound waves from the front and the back so they don't cancel out (no bass is the result). Make the board at least a 3 ft. x 5 ft. sheet.
Just load the speakers in and take a listen.
Here's a little trick for using a 4 conductor wire to use for all your wiring.