Step 1: Cut or rip your facing strip on straight of grain from linen or silk. Cut it 1" longer than your final length. Button and eyelet placket facings should be approx 1.5" wide and neckline facings 1" wide.

Neckline facings need to be much narrower than the other plackets because they are sewn on the curve. The wider your neckline facing the more you will constrict your bias cut neckline and run the risk of pulling at the shoulders or across the back.

Sew your facing strip to the right side of your garment seam using small running stitches. I use waxed linen thread for both linen and wool garments.

Step 2: Fold your facing over and finger press so that it now lies on the wrong side of your fabric.

Step 3: Sew the facing down with small running stitches.

Step 4: Fold under your raw edges and stitch down with runnings stitches

Step 5: This is what your right side would like. You may or may not use matching thread. There is no conclusive evidence that there was a concern about matching thread. Well into the 18th century formal gowns were still being sewn with white linen thread so the choice of matching thread is up to you. I used a contrasting color only to better show the stitches.

Step 6: For sleeve hems and using linen or silk facings, I fold over the hem twice.

Step 7: Sew down the sleeve hem using whip or running stitches making sure to close off the end so that your threads don't ravel.

Step 8: Here you can see a neckline facing over an eyelet facing. The only difference in how they are attached is the width of the facing.