This high fashion buttonhole treatment is a perfect solution when fabric is very dimensional and a machine stitched buttonhole that's not perfect can ruin a beautifully sewn garment.
1. To minimize the front bulk use a jacket pattern with a cut-on facing. That means the facing is one piece with the pattern and is just folded under at the vertical front edges.
2. Draw two lines perpendicular to the center front line.The first line passes through your bust point and the second line is 8-inches below the first line. These lines will become the horizontal seams that house the slot buttonholes. The seams can be sewn on the jacket front only or completely around the front and back. If the seams are to be featured around the circumference of the garment, mark the front pattern piece first and then align the back side seam with the front and continue drawing the horizontal seam lines in the same position so the front and back match.