Not sure if anyone else needs to see what is meant by a flange, so here is the link I followed to watch a U-Tube video.
http://www.quiltbug.com/articles/borders.htm
This reminds me of very fancy Victorian quilts which leave room for lots of cross hatching in the quilting, so you might consider leaving a fairly large white area before adding your next border.
With such a great start you can't go wrong!