Ended up spending most of the winter on the walls, working on warm days. Started by cutting and stapling sheet plastic over the frame where the walls would go.
Collected usable scrap lumber from around the property. Angle cut boards on the table saw to 30°. Made perpendicular cuts in the workshop with hand-held circular saw.
Started on the west wall. Didn’t beat the snow. Got most of the west wall nailed into place standing on saw horses. Finished on the extension ladder.
East wall was the most complicated. Hung the entension ladder on the roof peak from the foot of the banking, being careful of the picture window.
Made a platform with the ladder, to get the board above the window nailed into place. Steadied the ladder by running ratcheting straps out from the side windows, and finished the roof peak late one night in February under freezing drizzle.
South wall easier. Stood on the block of styrofoam from the picture window installation to get the top board in place. Worked up from the bottom. Recut the final board a few times.
North wall finished last. Cut the final board trapezoidally by hand.
Finished this afternoon, in sunny 45° spring weather.
Caulking needed in places, but walls are in place.
