As fun as it may be burning rubber is very useless and expensive. I had kids ask me to do this in my WRX as well.
if you want the easy way, you can just rev it up and slip (lift off) the clutch fast. If you dont like your transmission you can just side step the clutch (slip foot to the side and let clutch "pop" back up). I think the Boxster has enough juice to burn that way.
Just make sure to turn off traction control. I have not really tried this in the Boxster at all and I dont think I ever will. I have the optional 19" Carrera S wheels and well those tires grip and are too expensive to mess around with like that.
-aren