Its ridiculously easy cos its pretty self explanatory, I copied it from a picture I found on tumblr
1. Get a pair of leggings (colour of your choice)
2. Get some chalk (I used pencil but it didnt show up too great)
3. Draw outline of skeleton face like in the pictures I have here (I couldn't be bothered doing each individual tooth so what i did was just draw a smiley face line and then cut teeth randomly above and below the line
THINGS TO REMEMBER
The holes will be bigger than you originally intend cos the stretchiness of the tights will just expand that way
Dont cut the holes too close together cos the fabric will pull away some threads and may make one massive hole you dont want