When I "ground sit" I try to find a large trunked tree or a downed large tree as a back stop. A downed tree makes a good hide especially if you can snuggle up into the crown. As far as builfing a ground blind, I don't get too fancy. I'll clip a few branches or construct a quick surround using dead limbs. But nothing fancy. I'd figure if you go through a lot of trouble to build a fancy ground blind on public land, it is likely another will come across it and put it to use as well. Might even beat you to it ! And then what ?