Several tills can be glued on one piece of cork oak bark. A hook is then put on the back of the bark and the whole thing is hung on a nail!
I recommend that you use the adhesive GOOP. There are a number of forms of it. Choose one that you think is appropriate after reading the label. I of course use one that is waterproof. Liquid Nails is supposed to do the same thing.
Do not use hot glue. It becomes brittle and you'll find the plant on the floor! I also strongly recommend against any kind of metal. That green plastic covered florist wire is OK.