Step one: Cut out all your pieces.

Cut two of outer and two of lining. I had a 9 inch zipper so I made my pieces 9x6 inches. Adjust accordingly to how long your zipper is and how long you want your pouch to be, accounting for the square bottom.

Step 2: Attach the zipper.

Sandwich your zipper between a lining and outer piece and sew on the top edge. Do this for both sides of the zipper. Make sure the right sides are facing together and that your zipper is facing the right way.

Step 3: Iron it all down flat.

I’m pretty proud of my pattern matching here but it’s really irrelevant. 

Step 4: Place the right-sides of the outer together and right-sides of the lining and sew around. 

Leave a space in the lining so you can turn it inside out later. Also you will want to unzip your zipper half way before you sew. Pay attention when going over the zipper bits. Also if you want a tab in you bag now is the time to put it in. 

If you are happy with a flat bag you can turn it inside out and be done. If you want a square bottom, continue.

Step 5: Measure for the bottom and sew.

I decided to do one inch in. Mark where you would like and then turn the bottom so the side seam and bottom seam match up.

Sew on the line you just drew straight across, cutting off the corner. Clip the extra.

Do that for all 4 corners. Your bag should look square-ish.

Step 6: Turn inside out and sew up the whole in the lining.

Whipstich that bad boy.

Done.