No, I'm not talking about getting married.
Since developing plantar fasciitis in one foot I've learned that trying to walk on cold feet in the morning is a very bad thing. So I was thinking about buying some down booties, or just wearing multiple wool socks when sleeping in cold weather. But yesterday I had a thought that might be a better light weigh, low pack volume idea. I'm sure somebody else has already thought of it, and maybe determined it's a poor idea, but here it is.
Use polyethylene foam (PEF) as an insulator, either next to your skin with a sock over it, or between 2 layers of socks. As a test, I took a sheet of 1/16" thick PEF and traced the outline of my right foot. Then I rotated the PEF sheet 180 degree and took my left foot and lined up the toes with my right foot trace, and traced that foot. The left foot tracing is so you can fold where the toes meet and use that part as the upper covering for your right foot. (Of course the top part only needs about 1/2 the length of your foot.) Then I extended the width of the left foot tracing by about 3/4". Now I cut out my pattern.
To wear it I put my right foot down on it's tracing, and fold over the left foot part on top of my foot. The extended sides help to cover the sides of my foot. Then just slide a sock on over the top.
I immediately feel the heat being radiated back at my foot, and it doesn't feel that bad, even directly on my foot. They weigh next to nothing, and don't take up much space when folded up.
I expect they wouldn't last a long time, but who cares, it's simple to make more from packing supplies.
There would be many more ways to approach this including maybe wrapping your foot with a 2" wide strip, kind of like a cast. Another option may be finding a bag made of PEF that fits over your foot.
I haven't tried it yet while hanging, but I bet there are other people who can try it and improve on this idea.