Here's a video of the making of a no-sew flannel pillowcase for my great neice, Eva.
It's extremely easy. One hint: don't do what I did. Make sure that you line the cut strips up exactly before you start tying the pillow case together the first time. I had to untie mine and then tie it again. It came out really cute, mostly due to the charming print by Debbie Mumm. Flannel pieces were purchased at JoAnn Fabrics.