1. Ideally, find a low-angle slope (15 degrees or so) with a five-foot base and chunk-free powder. Start out facing uphill. Remove the snow in front of you until you've carved out a platform and are facing a wall four feet high.
2. Start tunneling into the bottom of the wall to make a door. The tunnel should be a little wider than your shoulders with your elbows slightly out. Dig straight into the hill until your torso can fit inside. Work slowly to prevent overheating and getting soaked by sweat or melting snow.
3. Dig up and forward to hollow out the main chamber. Keep the sleeping platform higher than the top of the door to trap heat. It should be flat and just big enough to allow you and a buddy or twono moreto lie down.
4. The walls and ceiling need to be arched and at least 18 inches thick. (Measure with a probe if you're in doubt.) Allow about six to eight inches of room overhead when you're sitting upright in the center.
5. Stick a ski pole into the ceiling at a 45-degree angle, handle down, to create an air vent. Keep it in place overnight. If it storms, you can open the vent without exiting by pushing the pole up so the basket clears away the snow.