One small tin can (I used a Vienna Sausage can)
Essential oil of your choice
Good scissors, tin snips, or other cutting device
Can opener that opens cans from the side
Step 1: Get a can
Step 3: Cut
You could get all fancy here and cut stars and happy faces and pirates (whatever you fancy) into the can. I didn't. I just wanted my bathroom to smell better.
Step 4: Light it
Caution: Hot things are hot, be careful.