I think I first saw this on Pinterest and it was timely as my Chives were flowering :) I googled it and found these instructions and images delightful.
I did not have near the volume of flowers that were used in the example but my vinegar is still turning a lovely shade and smells divine!
I added a couple of flowers later in the process, ones that opened after my initial harvest, they have just made it a shade darker. I'll let it steep a little longer due to the additions and am thinking this would make a lovey Christmas gift in a pretty bottle. :)