The board he used is a 1'' x 6'' x 24'' pine board. He needed 24'' because he had to have 16'' of stitches for the wing, and the extra could be used on the tail. Drive nails in every 1/2'' along the outside of the board, 1/2'' in from the edges.
Now cut a sheet of clear plastic that will fit between the two rows of nails. With the board laying flat on the table you will see the long board with nails' heads sticking up at you on both sides and a strip of plastic to fill the center region. [See figure, above]