I agree with Aria. Measure the center and, not the ends, but at the quarters, then average. That measurement will make it easier to ease the border to the quilt. When I pin, I pin at the center, the quarters, and if it is a very large quilt, I will also pin at the eighths. Do this to the border strip also. This helps to manipulate my ease in each section. I also use a bamboo skewer to help hold down the fabric (and it can also help scrub some extra fabric into the ease without puckers). Hope I explained clearly.