I suspect the BFL can be raised into position with a gin pole or similarly simple application of pulleys, ropes and poles.
If it's a truly simple structure destined for a 2 year usable life, I'd think the overhang wouldn't need to be as extreme as shown in Paul's side view. Or the interior could go further out towards the light.
If the slope of the side logs is quite flat it
should be able to keep soil on it. If it's more like a traditional A frame I'm not sure how you hold the soil on there.
For the triangle lovers out there, remember that triangles are extremely strong if you don't put a huge load on the sides of them.
Glenn, I like your sketch. If the building was built into a significant
enough slope, the ridge beam could be nearly level and the dug out floor could as well.