This is a good short video we found on improvised shelter construction. Big takeaway is be creative and remember insulation considerations. The video is not a full blown “how-to”, but it’s a good start. I would also add that when building a shelter like these (they are very camouflaged by default), I would hang my orange vest outside the shelter and hang my signal mirror also, to make it easier for help to find me if they were searching and I was asleep or incapacitated in the shelter.
The fellow that did this video has some good suff on his YouTube channel.