What you'll need:
A piece of fabric
A cord or something to use as a drawstring
Some cotton, needle, scissors
A stencil drawn on card
Optional: Pins, sewing machine
Step 1: The Stencil
Just trace around the piece of card (made from an old cereal box). Take a look at where to sew and the next steps will show you the order to do them. You don't need to draw any other lines on the fabric, but it's useful to use the card as a reminder, should you wait 3 years before you do another. :P
Step 2: Sewing the Top With the Drawstring
This can be done easily with a sewing machine, too, but I don't have one of those. I like to get down to the basics as I'm a bit of a rugged sort of chap. :D
This line of thread you'll want to do the most carefully as it is the only one you'll see when it's finished. I found this out after I'd done it but hey ho, we learn from our mistakes. ;)
After you've gone across to the end, go back again to fill the gaps, as seen in the third piccy.
Step 3: On the Edge
Be careful not to pull the thread too tightly or it will affect the shape of the pouch. And you wouldn't want to do that now, would you?
You don't need to worry if the line isn't perfectly straight as this won't be seen when you turn it outside in but best to keep it more or less straight.