After watching the video of how Sandra Betzina does the flat fly front, I tried it on my muslin #2 (in search of the perfectly-fitted pair of pants). It was easy to do and it worked out perfectly.
I drew the top stitching line in pencil since this was a muslin and it didn’t matter – obviously I’d use chalk or some other erasable marker to draw in that line on a real pair of pants.
You see the centre line because I had to attach “fly” flaps to the centre seam in order to execute the technique but on my next muslin I will incorporate the fly flaps into the front pattern pieces as you can see on Sandra’s video,
Because my memory is not as good as it once was, I thought it would be a good idea to create a set of written instructions for doing this instead of having to watch the video each time I wanted to sew a fly front. So I took a series of screen captures from the video and created myself an instruction sheet.
Here is a link to the video: http://www.threadsmagazine.com/item/3831/video-an-easy-flat-fly-front-zipper)
Here is a link to the instruction sheet I set up for myself.