1. Fold your fabric in half and cut out a quarter of a circle on each end where the neck hole and tail will be.
2. Sew (red) about an inch or so around the collar, so that there is a "tunnel" for the elastic to go through.
3. attach the elastic (or ribbon) to a safety pin and feed it from one end to the other, until both ends are protruding from the neckline (blue)
4. hem every raw edge (if you're particular, but this is optional since it's just for your cat
5. Tie elastic, so that it slips over your cats head, but make sure it is not too tight!
6. Apply to cat, pray for success
7. Take photos
8. For the hat, it's pretty open to any sort of cat sized chapeau, as long as you leave ear space. Maybe holes could be cut for the ears to stick out of; I have not tried this yet.
Tips: Do not just grab your cat and force this on them.
Praise and pet them before you put this on your kitty, and then tell them how good they look in it! :)