I wasn't able to complete all my samples in classes (too busy talking--making new friends and catching up with ones I only see once a year), so I'm making sure I do it as soon as possible so I don't forget what I learned.
One of those techniques is a foolproof welt that Kenneth King showed us in his "Cool Tricks" class.
This can be used for pockets or bound buttonholes--just vary the size of ribbon you use. I used grosgrain in this example, but petersham would work better and make a softer welt. You can find his detailed instruction in his book, "Cool Couture".

Lay the ribbon on the wrong side of the welt fabric and stitch 1/8" from the ribbon edge.

Fold one side over the ribbon and stitch between the first two rows of stitching.
Trim close to the stitching line
Repeat for the other side.

Lay the welt on the fabric piece with all 3 stitchlines facing up.
Stitch 1/4" from the outside edge of the welt.

Cut down the center of the welt. Do not cut the fabric underneath.
Cut the fabric from the wrong side, make long slits towards the corners.

Repeat for the other end.
Done!
Check out Kenneth King's website for more information on his custom work, articles and books. If you get a chance to take a class from him, go for it. He's a great and entertaining instructor.
Many thanks to Kenneth for approving this post!
Juliette