I used three layers of green felt, a simple stretchy headband, some silver beads, and hot glue. I freehanded my shapes, but you could use cookie cutters, flower patterns found online, etc.
(These pictures aren't the best-- my apartment has very poor lighting for photography...)
And while I was in the crafting mood, I also took about five minutes and made this simple yet cute "Pot o'Gold" for my classroom.
We are going to have a rainbow scavenger hunt, where shamrock clues (in the colors of the rainbow) will be hidden around the room and eventually lead the little ones to the treasure! I can't wait!