This is done from a tutorial on HonestlyWTF (I love their DIY's!) I used some black faux leather fabric I had kicking around, and a stud from my DYI Studded Denim Shorts Project. If you don't have a leather punch (I love mine), you can use a regular paper hole punch. If you don't have leather or faux leather handy you could use felt (like the tutorial suggests) or anything that doesn't fray.
Here's my final collar: