I used these instructions. I followed them loosely once I got the general idea. Because mine will be used for decoration only I hot glued the corners instead of using a pin. In the future, I'd like to use patterned card stock. These could be a great party favor or craft at parties. You could make miniature versions and adorn them on frames or vases --- or really anything.
I used off-white and yellow opalescent card stock. For the stems, I used wooden skewers. I recommend making pinwheels of different sizes for variety if you are making a bouquet.
Something else you could do with these guys? Skip attaching the stem and flatten them. Arrange them on white paper and frame it!