Some builders use a soundboard, some don't. It depends on the inside cut your using in your pots. The soundboard controls the tone of a call, it gives the call the sound your looking to get out of it. The tone is controled by the spacing between the playing surface and the soundboard. If you have to large of a space you'll get a deep tone that has a flat sound to it, if your spacing is too thin you'll get a high pitched sound that doesn't have much of a breakover in your yelps. That is why you'll see a lot of different materials used for soundboards. glass, slate, wood, acrylic, copper, aluminum, brass, titanium, each gives you a different sound to your calls. The height of your soundboard pedestal dictates the sound of your breakover, the sound of your rasp, high or low pitched rasp, a 64th of an inch makes a huge difference to the sound of a call. When your first starting to build calls it will take a few calls to find what works best for you. Keep notes of what you did when building a call, the height the your pedistal, the thickness of your bottom, the size of the holes in the bottom, the pattern of your holes, the thickness of your sides, the depth of the call body, the space between the surface and soundboard. Then once you've found what works for you, then you can start with different woods for your pots, and the shape of your pots.
Everything you do to a call has an effect to the sound of it, the glues used to glue it together, the finish you put on it, the wood it's made from, the shape of it?
Some builders find a combo that they like right away, some never find it, it takes a few calls to find what works for you, and good note taking, until you've built enough to know how they will perform?