Here is a good post on making a resin pendant, or resin jewelry in general from Jean Campbell at Beading Daily. The opportunities are endless of what you could create with this technique.
For complete instructions on casting with resin read these Basic resin casting techniques
Here are our favorite supplies for using resin when casting, Casting Resin
Disposable Mixing cups , Silicone resin molds, Items for Embedding
Cindy Lietz, Polymer Clay Tutor says
I’ve seen a couple people use this tape trick and I think it is an awesome idea! Of course making sure the tape is properly sealed is a must, since seeping out underneath would be a pain. It is such a clever way to use open backed findings though and creates so many creative opportunities. Love it!