I have been using a pretty simple method for the last several years and it seems to work well. I got this idea from Sue Raker - a Keeweenaw Master Beekeeper.
The sawdust or wood shavings ( I use planer shavings) act as an insulator and absorbs hive moisture. There are certainly more complex methods but this does the trick for me. By mid to late December my hives are pretty well buried in the snow - which acts as a great insulator. When I put mine to bed in the next couple of weeks, I will show how I keep an air space at the bottom and what I will do with my top-bar hives.
See video for overwintering demonstration.