Did you measure down the middle of the quilt? Then the two sides? Figure out the average size and then cut the borders to that size. Pin the border sides on, may have to scrunch or stretch a little. Sew them. Measure again for the top and bottom, do the same again, scrunch or stretch. Should have a flat quilt. Look it up on the U Tube for pictures. Also, crosswise fabric stretches a little, so if you have the material, cut on the length of the fabric. I like the colors of your quilt.