This one is another great idea from Elise at Grow Creative. She uses stencils with her watercolors. I would have thought that it would have just made a big mess and that the water would seep under the stencil, but that's not the case!
I got these Martha Stewart stencils at the craft store and I really think they are perfect for this technique. They are adhesive, so you don't have to worry about holding the stencil down tight. And you can just leave it in place until the paint dries so you don't have to worry about the paint smudging. I thought that the adhesive would wear off, but it didn't at all. I even rinsed it off in the sink, dried it with a paper towel, got paper towel stuck all over the back of it, re-rinsed it in the sink, and it is still as sticky as when I pulled it off the plastic. I got the flower set and I'm thinking about going back for another.
I just rotated the stencil to make all the flowers look less uniform and I used a black felt-tip pen to do the center of all the flowers.