My son's beloved lobster, Larry, recently lost his eye after our dog found him all alone in the living room. :) In an effort to make him more comfortable with his injury I made him an eye patch.
cardboard (for template)
black embroidery floss
If necessary, sew the eye hole shut with embroidery floss. (I made an "x" where his eye used to be, like they do in cartoons.)
Create a template using a thin cardboard. Cut it out.
Use the template to cut out 2 felt shapes. Sew them together with embroidery floss, using a backstitch.
Attach the eye patch to the stuffed animals. I used small stitches around the outside of the patch, to hold it securely. Then I used long stitches in the corners, to give it the appearance of having a strap.