These are the two front pieces sewn to the front edge of the side piece.
For pattern pieces in pairs (like two front and two back), use the first cut piece as a guide for placement of second piece to ensure the fabric patterns match.
The front piece matching with the front facing.
I thought the instructions for the welt construction were more than adequate. The key is accurate marking of stitching and cutting lines.
And now for photos of the finished garment.