I had fresh flowers in my hair. I had sort of short hair, so no up-do's. I needed a headpiece.

Here's how we did it.

I bought a plastic headband, and cut the very ends off, so it was just long enough to hold on to my head, but not so long that it stuck out below my short hair (the ends sort of disappeared under my hair, this way). I covered it then with fabric from my dress (cut a strip, wrapped it around, and sewed it on the back side.

Then, my florist took 3 white roses, and laid them in a row, and taped their stems together (she used white floral tape), close to the buds. Then she trimmed the stems so the last one about about 2.5 inches.

She used white floral tape to tape the stems of the flowers to the headband. She positioned the flowers down right next to the headband.

I fluffed up my hair around the headband to keep it from being too stark.

It looked really GREAT!

I'm not sure that you could be terribly successful making a headpiece ONLY from flowers; you'd need some sort of structure--even if it's only floral wire wrapped tightly around them to hold them in place.

There are lots of different headpiece styles you could find to use as a base to attach them to.

You are talking about small and rather large flowers. I would go with the smaller versions. If you are wearing a veil, they would look nice along the back of your head with the veil dropping from the flowers. If you have long hair, they would look pretty with a French roll and tucked into the "seam" of the French roll. Same with a chignon or an up do of curls, tuck the flowers into the base of the cluster of curls or the chignon. If your hair is long and will be gathered at the back, put the flowers there. Just be careful if you are wearing the flowers on top of your head as sometimes they can be too large or poke out the wrong direction. I suggest that you try it before making your decision in a practice dress rehearsal.