Nice movie, thanks for posting.
The method I like uses a post and rope. The post is the center. As the blocks go up, the rope (or cable) is used as a mobile radius to set the circular placement, and also set the block edge angle when one end is tied where the post meet the snow surface. As the rope goes around, it gets progressively shorter, winding around the post, which basically describes the desired hemisphere at the free end of the rope. For those of us who don't have the experience, skill and talent to build freehand, the rope provides a reference which makes the system a bit less prone to trial and error - especially if one is tired, cold, injured, etc.
I also wonder a bit about the floor. Sure, I get the attraction of cutting the blocks from right inside the structure. However, cold air is heavier than warm air, and tends to flow downhill like a fluid. The insulated sleeping sleds look like a good idea, but I'm thinking it would be warmer if the floor had a mound, or a small stack of blocks to put the sleeper well above the snow level outside. That would allow one to set up a cold air drain too. Now, who am I to question the success of people who have been living that way successfully for eons? Maybe they already figured out there is no advantage or not worth the work, but at -40F, I would think there would be some payoff.
After all, HL Menken famously said, for every complicated problem there is a simple answer that won't work, but there is an old German proverb that says an old error is more attractive to many people than a new truth.
In any case, next time we get the right weather, I'll have to give it a try and see if I can measure, and/or feel, any difference...that is, long before I need it to stay alive. If there is enough winter left, maybe you will beat me to it Gerry :-)
DxG