The fly front construction for pants can be a little daunting, but once you get the hang of it- no problem! If you have never done, or are a little rusty, do yourself a favor and do a trial run and work out the kinks. Here is my advice on how I insert my fly fronts. Let me know if something sounds confusing and I will clarify further. The guidelines below assume you have serged all of the necessary seams and joined the left and right legs together at the rises, stopping for the fly front insertion.