This is written by Christine Down. Christine sells instantly downloadable bag making patterns at https://www.sewlush.org/
If you missed the previous parts of this series find them here:
Work out how big you want your pocket to be. A pocket that is quite wide can be divided into two by sewing a vertical line down the centre of the pocket. Apply medium iron-on interfacing to both pocket pieces. Place pieces right sides together and stitch around all sides leaving a 5cm gap at the bottom. Clip the corners and turn out through the gap. Fold the fabric through the gap so it creates the appearance of a flat seam. Press.
Place centrally on the lining with the unsewn gap at the bottom. Make sure it is far enough from the top raw edge to accommodate your bag closure. Stitch around both sides and the bottom, triple stitching at both top corners.
Zipped Pocket Tutorial
You’ll need a zip longer than the pocket you are making, some fabric for the pocket and some medium/firm iron on interfacing.
Consider your bag design and decided where you want to put your pocket. Measure how big you want your finished pocket to be. To make a pocket pattern, add 1cm to the sides and bottom measurements and 2cm to the top measurement. This will be size of the inside pieces of the pocket. For my pattern I have used my standard measurements but you can make it any size that suits you using the formula above. You need to cut two of these in fabric and one in iron on interfacing.
Iron the interfacing to the wrong side of one of the pieces of fabric. Transfer the following markings to the interfacing. The markings should be in the middle 2cms from the top of the pocket. (Adjust the length of the sewing guide if you are using a longer zip.)
Place the fabric with the markings on the bag fabric where you want your pocket to be.
Right sides should be together. Pin into place. Following the sewing guide stitch around the rectangle marked on the interfacing. Carefully cut along the cutting line making sure that you clip right to the stitches on each corner. A seam ripper is an easy way to start to cut this line.
Remove the pins and push the pocket piece through the hole so that the wrong sides are together. Press thoroughly.
TURN THE FABRIC TO THE RIGHT SIDE. Place the zip underneath the hole and pin into place. (If you want to make this step even easier, use some Gutermann HT2 and glue the zip into place.) There should be an extra length of zip past the end of the hole. Sew around the zip from the right side using a zip foot. Stitch across the teeth at the end of the zip and trim the zip.
Take the other pocket piece and place it right sides together on the pocket. (This will be at the back of zip.) Pin together. Stitch around the entire pocket making sure that you only stitch the pocket layers and not the bag!