This technique explains how to insert a zipper into a single piece of fabric, and is often used for pockets in handbags, diaper bags, totes, etc. I use it for a pocket in my custom vendor apron, and it is very quick and easy!
The width of your fabric should be about 1-in. wider than your zipper length. The length can really be whatever fits your project. I'm using a 7-in. zipper, and my fabric is 8-in. wide, and 8-1/2-in. long. I have also used a lightweight iron-on interfacing to give my fabric more stability. You will choose the appropriate interfacing for your fabric.
My line is 1-1/2-in. down from the top, and there is about 1/2-in. on either side.
Carefully cut on the line, and your triangles. Fold the triangles back, and the long edges about 1/4-in. and press.
From the right side of the fabric, pin your zipper to the wrong side. (That definitely needs the picture!) You want to make sure that the zipper pull is completely free, and that you will not sew over the zipper stop on the other end. Using your zipper foot, start sewing on the end, turning the corners, and keeping the zipper foot even with the edge of the fabric fold. Remove the pins as you go. I like to back up a couple times on each end to reinforce the stitching.
Once you've sewn around all four sides, you're done!
A view of the inside.
This pocket is ready! I think it took me longer to write the post, then to do a zipper installation in this manner.
If you have any questions about this, please feel free to ask in the comments!