With building a soundboardless call, your almost better build them a trough call style, it will produce a much better sound than a pot style will. If you decide to build a pot call style, then you have to build it a lot thinner in heigth than a regular call, and thin the bottom of the call out to work as the soundboard, instead of a 1/4" thick bottom you may need to thin it down to 3/16 or less, depending on what the call is made of. Most boardless calls are 3-1/2 to 3-1/4 surface to allow the surface to flex enough and drowned out that high pitch sound you get with out having a soundboard in it, a small surface will be super high pitched because it's too stiff. If you use a small surface, cut out a piece of duct tape and stick it to the bottom of the surface, that will dull the high pitched sound and make it a bit better, otherwise your bottom of the call would be less than 1/16 thick. Take the DD Adams calls, they are about 3/8 to 1/2 tall because there's no soundboards in them, where a normal call is 3/4 to 7/8 tall.