Block your work before you sew it up, so it lays flat when you sew the sides.
Sew up the sides using a wool needle and yarn. You may also chain stitch the sides together, which I do, running the chain around the edge of the flap as well.
You'll see in the first picture that I have an opening in the bottom of the case for the headphone jack to plug into my Ipod. With a wool needle and yarn and using the whip stitch, I create a circular opening in between 2 single crochets.
Here is a picture of the circular opening from another one of my cases so you can get the idea. I push a pencil into the hole to shape it. Then, I spritz it with water leaving the pencil in until it dries to make a sturdy opening.
That's me this Fiber Arts Friday. See more fiber creations at Wonder Why Gals!