Carolyn from Handmade by Carolyn shows how to make a double welt pocket with a button loop. You can use contrasting fabric for the welts, as she did, or the same fabric as the rest of the garment. For a closure (optional), she sews a button loop into the seam for the top welt. Go to Handmade by Carolyn for the tutorial.
[photo from handmade by Carolyn]