Fold the inner open lining underarm seam and sew closed.
Using an iron press carefully, keep a linen or cotton cloth between the waistcoat and iron.
Mark front left for buttonholes and sew. I like to make a cardboard template for marking my buttonholes from the positions on the pattern.
Apply fray check before cutting buttonholes open.
Take the waistcoat front with the buttonholes and overlap it on the side that will have the buttons. Align the two sides as they will sit when finished and then mark for buttons.
Then hand sew on buttons where you have marked.
That’s it you’ve finished.