I like the yoke treatment on this blouse because the yoke edges are all finished before the sleeves or body are attached with hand stitches. Here’s how I think it was done:
You can see in this photo that it looks as if the yoke pieces were seamed to the lining (which is a slightly different fabric, a little coarser) right sides together, and then the piece was turned right side out. The pleated body and sleeve tops are whipstitched to the finished edges of the yoke.
In the above picture, the long top edges of the front or back yoke piece is turned under and pressed, then, right sides together, the piece is seamed on the sides and bottom. This piece is then turned right sides out and pressed.
Another possibility, shown below, is that the yoke piece, right sides together, is seamed on four sides with spaces left free from stitching on each side of the top for the straps to be inserted, then turned right side out.
The straps, shown below, are seamed, right sides together, on both sides, then the tube is turned right side out.
The ends of the straps are inserted into the front and back pieces until the straps are the correct length, then the top of the front and back pieces are topstitched close to the edge catching both sides in the stitching. Now the yoke has all finished edges.
Above you can see the topstitching on the wrong side where the strap is inserted into the front piece.
Tomorrow I’ll show the gusset, sleeves, and side seam.