Although I think some variation of this project is in the DIY book Sew Subversive, I used the directions from ReadyMade magazine. Completely skeptical that this project could produce a skirt, especially not a wearable-in-public skirt, I had low expectations. But it worked out. Check out the directions here to see how simple it is. I don't think this would have worked with a regular cotton pillowcase; the jersey material gives a little extra stretch to the skirt. Methinks that the Sew Subversive project might have tips for using two pillowcases to alter the size of the skirt... seems a bit more realistic than cramming yourself into one pillowcase.
It literally took about 10-12 minutes to make. Would have taken longer if I made the drawstring out of the jersey fabric, but I just used brown ribbon instead.
PS- I'm growing tired of these mirror self-portraits too.