Reading about recent projects, it sounds like some folks are struggling a bit with vest pockets. I hope the following tutorial will be of assistance. Comments, additions and corrections are welcome.
We begin with a picture of the left vest front. The basted lines are the pocket placement marks from the pattern, and the chalk marks the welt seam lines (1/2" lower).
The material is a striped silk, and the welt stripes need to be matched for a good appearance. A duplicate welt pattern piece is cut out and placed on the front, matching the seam lines:
The stripes are now marked on the welt. (Note: the seam line should still be matched; I moved it before taking the photo.)
The welt piece is cut out, turned over and pinned on place. The narrow center stripes make precise alignment easy in this case.
As a final check, the welt is basted on and pressed up. Voila! Matching stripes!
The welt is pressed flat again and sewn strongly to the front. A linen stay is added, clear of the seam allowances, to bulk out the welt (this is not needed if thicker materials are used). It will be retained by the topstitching, but is basted for now.
The back half of the pocket bag is placed ready to sew, a little shy of 1/4" from the placement line. The white chalk lines mark the seam with starting and stopping points. Notice this seam is a little shorter (1/8" each end) than the welt seam.
After sewing the back bag seam the pocket is slashed open. The placement line is used as the slit line but not full width. Clip carefully in a diagonal direction to the four corners.
This picture is of the inside, showing the edges pressed open. The welt seam is opened and one half pressed down. The diagonal slashings in the corners are pressed open.
The welt edges are now folded in, and the welt pressed up. The top of the finished welt is marked in chalk:
The welt is now tucked through the opening and pressed along the chalk marks. Ragged edges peeking out of the sides will be dealt with later
The pocket bag is now pressed down, then pulled through the pocket opening (welt partially unfolded for visibility):
To be continued...