Mine aren't quite that "sophisticated", easier to sew most likely. For one thing, I don't have the flaps on mine. But I do enlarge the bottom of the pockets with pleats or gathers so they will hold larger objects (not flat). I'll put them on as soon as I get a picture. Also use lots of velcro (the heaviest you can find) around the top, bottom, and a bit on the sides.
Happy Sewing,
ConnieKat