Here is what I did:
I started by taking lengths of black shoe string licorice and cutting them into 1 1/2" long 'legs' for the spiders.
Then I twisted open Oreo cookies. I found that if I put them in the microwave for 5-7 seconds, it made it so much easier to open, and I had way fewer broken cookies.
Put the top back on.
I chose to use red mini-jelly beans for eyes. They could look like angry eyes. Using a knife, put a bit of icing on the jelly bean to make it stick to the cookie.