All you need are a few fake flowers and a stretchy fake hair braid. (I got mine at Sephora.)
Chop off as many flowers as you would like to add to your braid, leaving about 1.5-2" of stem. Here's why...
You're going to braid the stem through the braid. This picture is just to show you, but I pushed the remaining stem through so it wasn't showing so much, and for hold.
I added 4 flowers to mine. It was a nice little detail to add to a messy ponytail.
I like this DIY because it just adds a little something extra but you can always take the flowers out and revert back to your basic braided headband if the mood strikes.