The first strip was bent around a series of nails .to hold the curvature. The strip was nailed at each end, outside of the length needed for the side. The second strip was bent around the first strip. Notice the quart cans in the first photo, that's old varnish cans filled with lead (~25lb each). I'd glue up about 4 strips at a time, bend them around the first strip, put a 2X4 with a lead can on top to keep them from flexing up, put clamps between the lead cans to keep them tight and, finally, put a nail in each strip at the end, outside of the length needed for the side.
It was a fairly slow process and would have gone faster had I nailed or stapled the strips down, but I didn't want the holes.