Please forgive the cell phone photos, I will have my daughter take better photos of me when the weather is nicer.
I did not use a pattern and I didn't measure much, but I'll share how I made mine with you!
First I wrapped the fabric around my waist twice and cut, then I folded that in half and cut. Then I held one piece against me and cut just below where I wanted the length to be and used that as a template for the second piece.
If you do it the normal way instead of my half-assed way you would measure your waist and cut two pieces of fabric (one for the front, one for the back) using the following for the length measurements:
Slide your elastic under the band and stitch the opening on the band closed. I like to also stitch through all layers in one spot (side seam) to make sure my elastic isn't going to be moving around, I don't know if this is necessary, this is just how I do it.
And that's it! Super easy, wasn't it!? I've made the one and I can't wait to make more.