You have several options, all depending on the work you want to do and the look you want to achieve. Quickest, birth the quilt, leaving the edge as it is. This doesn't allow for much quilting, but you can STID around the flowers without shifting the material. Or, quilt the top, then trim off the edged even and bind as usual. If feeling ambitious, quilt the top, turn the backing to form a wide 'binding' and then applique the hexies to this wide binding. And the one that I think you really don't want to do, add additional 1/2 hexies to even out the edge. ALL options are perfectly fine, whatever you want to do is the correct way.