How can I give myself a short shag haircut?

I always cut my own hair and I know how to do a good layered cut, but I don't know exactly how they get that textured piece-y look. My hair is thick but fine, and naturally wavy. I want it to look like my avatar.How can I give myself a short shag haircut?
OMG, do not cut your hair yourself. It will be so uneven.

blush