How are these beads made? (not my work)

https://preview.redd.it/88wi7g3r2lae1.png?width=1448&format=png&auto=webp&s=4537d1d99098ea29462327b937c2d03796d3e233

It looks like the gems could be glued on? I read that they can be drilled and embedded but these look more like they are on the surface. I'm wondering if they are super secure that way? I'd appreciate any info on how this is done