There is a wrong way to write a Fringe play about how to write a play, as I learned last week. There’s a non-stop hilarious right way, too. Assembly Required keeps its audience belly-laughing and grinning from ear-to-to ear during the entirety of its 60 minutes. Brian Sutow and Joshua Morgan bring us Rob and Flick, a duo high on octane and chemistry, who tour elementary schools and other auditoriums putting on unintentionally inappropriate…