Wow love the pattern and colors.....seems like no matter what you do there is always quilts that do that.....
I too measure from the center and that is how long the strip is regardless....cut two the same wideth....fold in half and mark the center and mark the center of the quilt....I pin the centers together......and then match the ends....sometimes it behaves and lays flat and other times I halve to fudge the fabric in or pull.....a little to get it to sew right .......then repeat and do the length ....measure from the center side to side......cut two.....find the center and mark....mark the center of the quilt ...pin centers together and then ends...sew ......This is one of the things I have learned in a quilting class....."How to square a Quilt"........
Don't mean to sound like a know it all ....but you asked....I hope it helps......and it has worked really great for me......but I still once in a blue moon have some problems......Good luck and hope you try this idea......:-)....