Buttonholes should be overcasted or serged as soon as cut, with fine
thread or silk, the stitches should be light, loose and even, this is
done with a slanting stitch.
Making buttonholes: Insert the needle on the edge of the material and
when half way through, take the two threads at the eye of the needle
bring them towards you at the right and under the point of the needle,
drawing the thread from you, making the purl or loop stitch come
directly on the edge of the buttonhole. Stitches should lay close
together just far enough apart for the purl or loop stitch to form,
always have each stitch of the universal length so the stitches will look
straight on each side of the buttonhole, the stitches may be placed
closer together at the end as most wear comes there.