I use E6000 it works very well for the plates. I really like using the flat sided bottles much easier than drilling but they are hard to find. I grab all I can find at the thrift shoppes. Yes you can drill them also and there are quite a few tutorials on drilling plates if you search U-tube.
Not a glass plate flower but this craft project was also done with the E6000 glue I spread the E6000 glue on the glass and placed some of our beach collection in the glue then poured sand over it. The shells, star fish, driftwood, colored glass and sand all held very well and I was very pleased with the finished project.