A few months ago, my friend Leah introduced me to the no sew ring sling on Jan Andrea's site. In a nutshell, you thread the top part of the sling through the rings, just as you usually do the "tail" (see link for a much better explanation). The friction of the fabric on the shoulder should keep it from slipping. I eagerly made one for myself, using a soft lightweight fabric my mom brought back from Brazil. The problem was that it was shorter and not quite thick enough for me to keep secure up top (it is unlined). Then I thought of tucking the fabric through the rings one more time. The end result was this:
Not only does it look more like the sewn on rings, it works well for shorter, thinner fabrics. For a better understanding of what I did, I have provided the video below:
Especially with lightweight fabrics, inspect your fabric regularly for any worn spots.
UPDATE: Leah has posted a video on how to do the initial thread for the ring sling.