The following information is my notes from Sandra Betzina's demonstration with Ron collins, the most common-sense method for creating a welt pocket that I came across when researching the topic.
- Pocket piece = lining fabric. Pocket piece size = from side seam, 3/4 or so along the waist and down twice as far as you want the finished pocket to be (or cut on fold at bottom). At one end, on the back of the pocket piece, overlay a piece of fashion fabric about 4” deep and the width of the bottom of the pocket piece, over the lower end of the pocket piece and zig zag into place along the long edge. This will turn through the 'window' and face the pocket opening.
- Lay pocket piece over garment with back of pocket piece/overlay facing the RS of the garment, matching waist and side seams. Draw the window onto the RS of the pocket piece using chalk and interface behind the window on the garment. Use a grid ruler for accuracy. The window is usually about 6" x 1" long.
- Sew along marked line, using small stitches before and after each corner. Cut midway between the stitching lines, forming a V before each corner and clipping right into each corner, making a nice, fat pie at each end. If fabric is ravelly, dot a spot of Fray Check at each corner.
- Turn fabric through. From RS, finger-press seams in place, slightly favouring the RS and then iron in place.
- On long edges of box, on WS, press Steam a Seam. Put the 2 interfaced welts - 8 x 4” - RS together and baste down the middle. Turn so that each welt is folded back on itself, with the basting in the middle, and press hard. Position the welts under the box, centred, and press lightly under a press cloth. Lift edge of one side of window and position a fabric loop or ribbon loop under the edge then press hard, with a cloth, from both sides. The Steam a Seam keeps the welts and the loop in place.
- Can topstitch around the edge of the window OR can sew invisibly - to do this, lay garment RS up and then fold fashion fabric ONLY back to reveal the stitching line on the interfacing. Sew along the stitchin line, pivoting at the corners and keeping other layers OUT OF THE WAY! This will sew the button loop at the same time. Press.
- Remove basting line to open up the welts.
- Fold the pocket pouch up to the top, matching side and waist seams. Sew the free inside edges together and finish. Machine-baste along the waist edge. Press over a ham to get the body curve, not caring one whit if the side seams are out of whack. Machine baste the side seam.
- Sew button on seam for better anchoring.