Sure, I've made the traditional slap stick numerous times.  It's a good way to simulate the crack of a gunshot safely (with practiced timing, of course).  There are a few things to take into consideration when building a slap stick.  First, use milled wood (clear pine, birch, poplar, or maple works well) that is very flat, smooth, and around 3/4 inch thick.  I've found that the flatter and smoother the surfaces are, the 'cleaner' and more reliably the "bang" will sound.  You might want to round off the OUTSIDE edges of the slats to minimize the threat of splinters.  Leave the inside edges squared off for a sharper sound, though.  I've also experimented with other materials and always come back to clear (knot free) wood because of the strength and tonal properties wood has.  Another thing of importance is to use a solid, but free moving and SILENT hinge on the end.  One that will keep the two slats in perfect alignment with very little side movement.  The 'tone' of your bang is influenced by the material used and by the width and length of the slats (bigger surface=lower tone), so play around with strips to find the right sound you're looking for.  And finally, fashion some kind of handles on the slats to allow the operator to smack them together comfortably and without stinging his/her hands.  Locate them at approximately one third of the length of your slats, located closer to the hinge.  That will give you the mechanical advantage of getting a good, fast slap of the two surfaces.  Too far from the hinge and it won't be able to really 'SNAP.'  Good luck.  This is really a very simple project and won't take much time to do, so if it doesn't sound quite like you want it to, it won't take much time to try another configuration.  Good luck!