This is the picture I found on http://www.theknot.com/ to use as our inspiration, but I actually just used google images search with "sunflower bouquets" to find it. After finding this on the knot, I searched within for more sunflower ideas and I was very pleased.
This is the bouquet we came up with using flowers purchased from Michael's and Hobby Lobby when they were half price. We also purchased a bouquet holder from Hobby Lobby. It still needs ribbon and finishing on the base and I know we'll play with it more before next year. Over all though, I am very pleased with how it turned out. 
Attached to the bigger sunflowers purchased above were these smaller ones (how convenient!), so we decided to use them as the focus of some boutonnieres for the groom, groomsmen, fathers, speaker, ring bearer, and ushers. It looks big, but it's a really close up shot. We still need to pin one to a suit jacket to see how we like them, but I am again pleased for the time being.
Putting bouquets together is really very simple and something that can be taken apart and redone easily. These sunflower "stems" were pretty thick so we used a pretty heavy duty pair of pliers to cut them. You could also use wire cutters or heavy duty scissors, especially for the thinner stemmed flowers. The boutonnieres are held together with green florists tape.