I have seen these and think they would be simple to make.You can buy the pressed flowers at Wal-Mart or the craft stores.I think what I would try,since I don't have a drill for drilling holes in glass,is buy the cheap 3X5 or 5X7 wooden frames at Wal-mart or the dollar store,then have an extra glass cut for the frame.It would be very inexpensive.Take the cardboard off the back and clean the inside of the glass.Position the pressed flower wherever you want it on the glass in the frame then lay the other piece of glass on top.You can glue the glass in with a bead of silicone glue then add embelishments to the frame or leave it plain.Attach a hanger or a chain to hang it with.
Most glass shops will cut the glass to whatever size you want or you may find the sizes and shapes you need at Michaels or Hobby Lobby.
If you are using 2 pieces of glass,drill the hole for the hanger.Insert the pressed flower between the 2 pieces of glass.The 2 pieces of glass can be held together with a product called Copper Foil tape.I think it can be purchased at craft stores in the area where stained glass supplies are located.It is a thin strip of copper foil that has a sticky side that you burnish onto the glass.
Hope this helps............Lillie

Thank you Lillie. I like the idea of using a frame. Maybe that will be my first attempt. As I do stained glass, eventually I hope to use the copper foil method and then solder the foil. In that case, instead of drilling holes I'd probably solder a couple of hooks at the top. Will see.

Hope I'm posting correctly.