Hi Susan,
Yes, you’re going to need a mold for your project. Unfortunately, we don’t have anything like this in our store.
Once you get the mold, you’ll need to know how much it holds so you know which resin to use.
Since you’re working in molds, you need to use a resin designed for those. We’ve got two. The one you use comes down to how much resin you’re mixing and pouring at once.
For pours of 3 ounces or less, the Resin Obsession super clear resin is what you want: https://shop.resinobsession.com/collections/resin/resin-obsession-super-clear-resin
For pours of 3 ounces or more, the Resin obsession deep pour casting resin works great: https://shop.resinobsession.com/collections/resin/resin-obsession-deep-pour-resin
If you need help figuring out how much resin you need, our free resin calculator can do it for you: https://resinobsession.com/resin-calculator/
You’ll need to put the shells in while the resin is still liquid. Otherwise, you’ll introduce bubbles that likely won’t come out before it begins curing.
If you can’t find a bowl mold, here’s an article showing how to put shells in a resin business cardholder: https://resinobsession.com/resin-tutorials/diy-business-card-holder/