When you are that cold, its telling you to get out of the stand and hunt a different way….. sorry my usual rant of not camping in a stand for 3 months. Anyways, like said, thin wool then heavier wool sock in boot that is oversized for 2 socks. Also the over boots are great especially if you drop foot warmer into them. I've got 2000 gr Irish Setters boots that work great when its frigid. And movement every 30 min minimum to get blood moving. The other thing is keep rest of body warm. Keep head warm, I wear a Mad Bomber hat with real rabbit fur, forget the synthetic crap. And I wear a wool based thinsulate bibs and jacket late season. Super quite in the dead cold, and light colored to blend in with the winter woods better than the typical camo. I've sat all day at 15 below and its doable, but usually my ass is out of the stand, and still -hunting along a thermal thicket along lee side of ridge. Heck lot more fun.