There are so many options to this. You should do a search on borders 'cause there are so many things you can do.
If I cant figure the math for pieced borders to be exact, as in flying geese, I don't put them all the way around. I'll put corner blocks in or have the geese fly in two directions on each side and put a filler block in the center of each side or , or, or!!! Lots of options!
peace
Nativetexan has the good idea of adding a small sizing border to fit the geese. Also a great idea! Great example and nice quilt!