the problem with using HAY to make blinds is, MOLD moves in rather fats after a few months of sitting, there, a, replace every yr deal, not a set up and have for yrs deal!
and again, pending on weather, depends on how fast mold gets into things
if you farm, you should already know about mold on hay bales!
and breathing mold in is a risk, many folks shouldn't take IMO
a TIP if your going to use hay bales, place a pallet under things first, to get the most air flow on all sides of things
deer do get used to things fast, so set them up, as close to the season as possible, as to building them months in advance
a week or two is all deer need to see them and get used to things from my experience!