The directions for making and applying borders on this thread are all excellent. One time I couldn't measure from the center of the quilt because it was a twister quilt, and everything was on the bias. With that one I knew that each block was supposed to measure 4.5 inches, so I counted blocks and measured the borders. Worked very well.
But when I apply binding, I stretch it. Not really stretch hard, but I smooth the quilt edge out for the next few inches of sewing, lay my binding over that and pull, just a little, enough to make the binding taut. Then I put my finger down on that to hold it in that position and sew those few inches. Smooth the next piece of edge, lay the binding taut, and sew again. That way you are taking up the slack on the edge that the quilting did in the middle. I don't have wavy edges on my quilts.
(When I'm smoothing out the edge of the quilt, I have to make sure the backing is under there. Once in a while it decides to fold back away from the edge.)