I hunt out of a tree stand with a tarp around it and use a similar method. I have a small alcohol stove which is silent and scent free that I heat up some water for a cup of tea about 9:00. The stove sits on the floor of the stand so I can harvest some of the heat while my water is heated. I'll then use the hot tea in the cup to warm my hands while I sip the hot tea with a cookie or candy bar. I have had deer under my stand while the process is happening so it doesn't bother them. That little ritual will get me through a cold morning.