Imanit, Those sure look colorful in the photo.. looking forward to seeing your photos of them.
Lisa, Sometimes they do double drill button shape pearls so they will sit flat.. mostly in really inexpensive Chinese pearls. One time in Tucson I saw a strand of mabe pearls (maybe 14mm) double drilled to sit flat "collar-like" around the neck. The look was fantastic, and the drilling was SO precise, each pearl drilled at a slightly different angle to fit the neck just so... the price tag was absolutely comical... especially considering that these were high domed mabes with a flat shell backing, making them 80% glue and 20% shell. I think there was an interesting idea there with the incredibly precise drilling, just wished they'd used real pearls! Sorry it was so long ago, I didn't take any photos.