If you want to make a hem facing on your coat or jacket see the guides here. I use the CF (c) piece as front facing on version 2 and 3. Therefore, you need to make hem facing on pattern piece A-B-D.
Draw the width of the facing on to the bottom on the pattern pieces. The red line. I make the hem facing 5 cm wide. Then I also have for seam allowance
Trace the hem facings on to a new pieces of paper.
Cut away the seam allowance where it is shown on the illustration.
The two pattern pieces where the seam allowance has been cut away, you need to tape together
Now you have two hem facing pattern pieces. One that fits the side-front and one that fits the full back piece