The 2" jewelry molds work great to give a perfectly smooth finish on the front of your necklace, but they're not quite deep enough for this project.  Use a little bit of mold-making putty or sugru to build up the edges of one of the molds about 1/2" or so.  Be sure your extra walls are stuck down to the mold very well, so the resin doesn't leak out through the gap. 

Once the mold is ready, place your glass bits or diffusion materials in the bottom.  They shouldn't take up more than about 1/4".  

You want something that's opaque enough to hide your electronics, while being translucent enough to let the light through. I used opaque mosaic glass tiles that I crushed into little bits with a hammer.

Set your electronics inside the mold with the induction coil at the top and the LEDs lining the edges.  Be sure the induction coil is as level as possible, and that it is the highest point inside the mold.  Peek from underneath to be sure your LEDs aren't showing from the front.

Put on your protective gloves.  Following the manufacturer's directions, mix up the resin really well* and slowly pour it into the mold.  Try not to cringe as it coats your electronics in goo.   

*when they say mix for two full minutes, they mean Mix For Two Full Minutes.