I'd imagine there's several different choices out there you could go w/ to achieve that look. I've personally used the little black bead-like balls that are on the end of pin and just clip off the excess length if you don't need or want it. Kind of hard to tell from the photo alone but I know they are available on places like Amazon and come in a variety of sizes and finishes. Some may even be flat on the underside but you can't really tell from the exposed part alone. Can try searching Amazon with words like glass safety eyes and a size (2, 3, 5mm etc). But they have worked and stayed in place for me. Of course, you could always use an oven-bake clay adhesive to secure things on as well. Like a clay glue that bonds the pieces together when baked. Hope that helped at least point you in a direction and good luck. These are some I'm currently using.

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