Tacky Glue (brand name) has worked for me in the past. It will keep the stones from sliding around, is easy to reposition stones , drys clear, and does not react adversly with CA or resin. I have a photo in my album on site that shows a pen with Swarovski crystals and real gold filigree added over snake skin, and cast in resin, if you want to see what it looks like. A word of caution, carefully measure your blank with a calipers before casting so you don't cut the tops of your crystals off when you turn it down. Don't ask me how I know this, just take my word for it. Jim S