I found these great pendant tray castings on Ebay, sold in lots of either 5 or 10. I liked them for their size and the design on the back. Any casting tray will work or you can use resin molds for a free standing piece. You will have to drill a hole through it to attach a necklace or ring though.
I used a two step epoxy resin on these. I used Easy Cast brand. I can't make a comparison to other brands because I have never used a different kind. I will tell you it was easy to work with and did not have a strong smell. It hardly had any smell really. I of course held it up to my nose and took a big wiff, at which time there was an odor, but it didn't knock me out (I would tell you if it did.).
Mixing takes a little bit. You have to stir for two minutes, transfer to a new mixing cup and stir for an additional 2 minutes. They are serious about it needing to be mixed well. I didn't use a timer or even look at a clock, I just stirred till I felt I had stirred enough. I probably over stirred, but that can only be a plus, right? After all that stirring, I added some black dye and stirred some more. I then filled my casting with a thin layer of the dyed resin, just enough to cover the bottom of the casting. I wanted to leave enough room to fill it some more.
I let that dry over night. It doesn't need to be completely dry, just dry enough that it wont mix with your next layer.
For the pretty colors I used Little Windows Dichro-ish Glass kit. It comes with the dye I used for these pieces which is a black powder with some black glitter in it, and some shiny, colorful papery stuff, kinda reminded me of velum paper.
I chopped up some of the sheets into little pieces and sprinkled them on top of my castings. I wish I had used more and maybe cut them into different shapes. Most of mine are like triangles, I have a lot of pointy corners. Live and learn. I then mixed up another batch of resin but did not dye it. Pour that over the pretty pieces and let dry again. Keep an eye on them for a minute or so to make sure the flakes don't float to the top and stick out of the resin. I used a toothpick to push them back down. I still have a few small corners sticking up, but well, it's my first try!!
The instructions on the epoxy say it takes about 24- 48 hours to fully dry. If you don't mix it correctly it may never fully harden and in extreme cases will always stay sticky, tacky or soft. In my short experience it takes a lot longer than they say for it to fully dry, but maybe I'm not mixing it correctly. After I let these sit over night they were dry enough to pick up and touch, but will still leave a mark if you press your fingernail into the resin.
In the end you get something pretty and unique. I'm not completely happy with mine no matter how many people tell me it looks great. I'm my own worse critic. I can always find something wrong with what I do and can always think of a different way to do something. At least that way I never run out of things to create.