Since I blew SIL's purse off the other night, I HAVE to get my rear in gear and get her purse finished. I took pics as I made the zippered pocket. I sure hope these directions make sense. If they don't, LMK, and I'll try to make it more clear.
Step 1:
I use a 6x10 rectangle of interfaced fabric and a zipper that's at least 9 inches long, but the longer the zipper, the better.) DO NOT USE A METAL ZIPPER.
Step 2:
One one end of the fabric, make a small snip 1 inch away from the end.
Step 3:
Put your zipper right side down on top of the right-side-up fabric at the edge.
Step 4:
Use your regular presser foot as a guide. Put the left edge of the presser foot against the edge of the zipper. Move your needle as needed. Sew the length of the fabric.
Step 5:
Flip the zipper up and then sew along the edge, making sure to catch the fabric underneath. Line your foot up alongside the zipper and sew (as close as possible) the length of the fabric.
Step 6:
Leave the zipper flipped up. Now, flip the bottom of the fabric up and put it edge to edge with the zipper, right sides together.

Although you won't be able to see it, you'll be able to feel the zipper. Let your foot run alongside the zipper, as close as possible. Sew the length of the fabric. The zipper will be on the left of the foot.
Step 7:
This is what you have so far. Open the zipper and repeat step 5.
Step 8:
Turn pocket right side out, zip the zipper to the edge of the pocket and tack closed, hand-stitch or zig-zag. I did it in pink so you could see it.
Step 9:
Open the zipper and turn pocket inside-out. Leave the zipper open. Pin sides together, making the snips be the top of the pocket (zipper won't be along top edge.)
Step 10:
Serge edges together, letting the serger take off the extra zipper.
Step 11:
Turn right side out. I've found that making square, neat corners is easier if I fold the fabric to the inside along the needle-thread line.
Step 12:
Here's your finished pocket. It needs a good pressing, now.
