In my opinion flossing is just glorofied snagging. I basically consists of people snagging fish in the mouth, so it is considered legal if you catch one. Unfornately it is common pratice here in the Great lakes, that is why the chuck and duck method get so much critisim. Most people who floss use a long leader, small fly and bounce bottom, and at the end of the drift they will do a long side ways hookset. I'd imagine that there is plenty of this going on in PNW rivers also.