I bought a stem of fake orchids, disassembled them, put two together, sewed a few stitches to make them stay together, and then glued a button on the top (with Household Goop). And then I gooped the flower onto the headband. Easy peasy.
The next headband was a little different. I cut circles from different colors of jersey from old tees I've embellished (I used two tones of gray and black), folded them in half, sewed them together in the middle. Then I sewed a pink cultured pearl to the top.