My second attempt at these coffee coozies was much much better than the first (not documented for good reason). This was the first project I took on with my sewing machine and found out the hard way that mini Janome does not enjoy sewing over elastic hair ties.
The original tutorial from House on a Hill Road was really easy to understand. After my first go and the awful mess I made with the hair ties I decided to sew 2 buttons on the coozy instead of 1 and just wrap the hair tie around the buttons (instead of sewing them into the material as directed). So much easier!