I've used them, only in joining someone who had them. The traditional practice from what I understand is to beat in a path through dense cattails to isolated holes and visit the hole to hunt, key part being beating the path in the first time. Before the season. Following a path through a thick marsh is pretty easy but breaking a new path is a lot of work. What you are skiing across needs to be pretty consolidated, that is, open patches are problematic. The area I hunted was solid cattails an it was an efficient means of travel.
One other experience is that I have tried cross country skis and the work surprisingly well to cross the marsh, but again, once the vegetation becomes sparse, you can really get mired if a ski gets in the mud. Really mired.
To use marsh skis to get into an area like an island or hummock would work. I can't see how you could actually hunt from them.
The bindings on the marsh skis I've seen are just a rubber loop to shove your wadered foot in. They would not be hard to make. Given my attempts with cross country skis, I'd try them first, they are narrower and shorter, but they did work.