These are some craters I made using the AOL method. For those of you who don't know what that is, it involves getting your hands on an AOL CD(not as easy as it used to be), gluing some styrofoam to it, then painting it to look like a crater.
Just glue some styrofoam onto the CD(I recommend you shape the center of the crater before you glue it on), cut the outside slope to whatever angle you want, glue a small disk of card onto the center of the crater to cover the hole in the CD, flock, paint, and enjoy. These things are easiest when done in batches. Be sure and save the off cuts as well. I made this small crater from the center of one of the larger ones. Just use a piece of card as a base.