It's about as easy as a sewing project can get.
What you'll need:
one full size bath towel
one matching hand towel
sewing machine with a needle for heavy fabrics
What you'll do:
1. Pre-wash your towels and dry on medium heat. This gets the towels clean and the heat drying will help avoid any extra shrinking in the laundry later.
2. Cut the finished edges off of the hand towel on each of the SHORT ENDS, leaving the long edges in tact.
3. Fold the hand towel in half, shorter ends together. Mark the centers of both edges with a water soluable marker or pins. Place one side of the long edge slightly over the other and pin in place. Starting at the edge (instead of the point), machine baste together toward the point leaving 1-2" free. Top stitch with a zig-zag stitch setting your machine's stitch length short and the width at its widest. You've just made the back seam of the hood.
4. Turn to inside out with right sides together. Take a tuck across the point of the hood and pin in place, right sides together. Cut off the point so there is a straight line approx. 5" seam across. Sew a 1/4" seam allowance and press seam down. Zig-zag top stitch, encasing the raw edges.
NOTE: Unless you're using an industrial sewing machine, be careful when sewing over the pleated section as it could break your needle if you speed over it.
You're done. If you're an experienced sewer, it'll take you about 30 minutes to an hour. Feel free to add trims like chenille rickrack or cotton ball fringe to the hood or edges of the towel.