I'm going to start by apologizing for these photos. I used my backup camera and they're just not as nice as I'd prefer. Although these are just clovers from my yard, we can pretend that they're shamrocks.
I started with a base of sinful colors happy ending. There were some clovers growing outside so I picked and pressed them. To press them I placed them between two sheets of newspaper and put that in a book. I put a heavy object on top of the book for several hours. It helped flatten them nicely to make them easier to apply. I put a little bit of a clear top coat on the green before the clovers were put on. The whole thing was topped with seche vite which made them really smooth.
The clover turned a little brown when the seche was added.
I used to do this with wildflowers when I was younger. I think I'm going to have to start that up again this spring.