In response to comments from my first post:

The measurements and directions for the pillowcase are
so easy...just purchase 1 yard of fabric.  Fold it in
half, right sides together, stitch across one end and
up the side.  For the top casing, turn under 1/2" on
the top edge, then again 4".  Stitch the casing in
place, and you're done!
 
For most projects I prewash fabrics.  However, fabrics
are easier to work with (especially for kids) prior to
washing while there is still some sizing in them.
Always wash it after stitching and before using...you
don't need those extra chemicals on your face.

Enjoy!!