Silicone Resin Jewelry Casting Mold, Resin Jewelry Molds, for DIY Artcraft Project, Crafting, Gift Pendant, Pendant Earrings Making, Large

I would look for a cabochon shape, like this tray (link below) to use, it might have the right size/shape you are looking for. As far as yellowing, you are adding color so that shouldn’t be an issue. Practice with fireplace ashes, I’ve heard it’s the same texture. I used Diatomaceous Earth to practice. To attach, scuff up your item (for grip) then attach with resin or E6000. I’m not an expert but this should get you heading in the right direction. Good luck ✌🏼 https://a.co/d/06INaI9Y

For small amounts: Cabochon mold: https://www.amazon.com/Silicone-Jewelry-Artcraft-Crafting-Earrings/dp/B09Q2SQSNY Cabochon mold with bezels: https://www.amazon.com/Pendant-Teardrop-Silicone-Jewelry-Crafting/dp/B07K9JM6TM Pendant mold with holes: https://www.amazon.com/Resin-Jewelry-Molds-Silicone-Reusable/dp/B0F9DXGQXM