A dugout can be as plain or as fancy as you have time and energy to make it. To build one you will need to find a suitable hill to dig into. Try to find one that is not too hard to dig into and doesn’t have any large rocks above it that may roll onto your shelter.
Try to find a spot that when you dig 10 or so feet back into the hillside it will be above your head. You are basically digging a trench into the hillside, walling up the front with either logs or piled rocks, adding a roof and you have a dugout shelter.
The roof can be a ridge pole running from the back wall (dirt) to your front wall. Put more poles in tightly together, add a layer of pine boughs and then cover with dirt. The dirt you remove from your trench can be used to build up the side walls where the hill slopes down to nothing at your front wall. You will want to add a drainage ditch to divert any runoff around you dugout.
If you have the time, energy and resources you can build a stone fireplace and chimney along the back wall.
It is much simpler to build than a cabin, and it will keep you much warmer in the winter if you build it right. Mountain men spent many a winter in dugouts spread around the Rockies. While this may be a poor (or impossible to make) shelter in the flat lands, it really shines in hilly country.
The dugout is a simple shelter to make if you have a digging tool, and while I have never done it you might even be able to do it with just a digging stick. It will require more work that most primitive shelters but will pay many rewards in warmth and safety.
The other day someone asked my opinion of what the best cold weather primitive shelter was. My immediate response was the dugout. A dugout is simply a cross between a log (or stone) cabin and a hole in the ground.
A dugout, while more work will be worth the time and effort it takes if you plan of spending much time in it during cold weather.

He enjoys helping others prepare themselves for multiple dangerous scenarios, by coaching them on how develop their own customized survival & preparedness plans and develop their survival skills. He teaches his students and readers to make preparedness and survival knowledge part of their daily lives.