They're of a soft thin cotton fabric, with embroidery thread to tie around the waist. The fabric is teal, but looks more blue in the photos. I'm using a webcam for the photos in this post rather than my phone, so the pictures in general will be uglier.
Below the cut is an explanation of how to put the wrap pants on, and the pattern so you can make your own.
(The shirt in these pictures is the undershirt from Eun-jae's very first post.)