After doing the center of this quilt it really was just about getting the boarders on. You'd think that, that's the easy part and while you're right it is, there's a right way and a wrong way to go about it. If you haven't taken a class or read anything about adding boarders, you may think that you just measure out the fabric and slap them on. However if you choose that method and send your top out to a 'longarm' quilter, you may find she's not so happy with your top. If you don't measure properly your quilt will not lay exactly square and will give her problems on her quilt frame.
When you sew a new boarder onto your quilt, you need to treat it as if you're just adding on to another block. Which indeed you are! For my interior boarders I was able to add them without having to use more than once piece of fabric, but as I added the more outer boarders I then had join pieces together.
When I do this I join my fabric like I do when I'm making a binding, by adding it on in a diagonal. I place the fabric in a 'L' position, mark the diagonal, sew and cut.
Then I cut a 1/2 seam allowance and press the seam open. This gives a bit stronger seam.
As always enjoy your day!!