Never fail - easy peasey mitered corners
Someone showed me this fool proof method, and it works.
1. leave about 4 inches on each border top, bottom and sides.
2. At one corner fold the top 4 inches over the side 4 inches,
then where they meet and cross over the other -and
on the very outside edge of your corner, top where they cross,
make a small - - angled / --- a 1/8 or 1/4 inch snip toward the corner of the quilt with your small scissors, in the outside corner of those two border fabrics, snip through those two at the same time (do not snip on the quilt corner)
Now On the wrong side of your border fabric pieces....
draw a straight line down from the snip to where the quilt corner meets the border on both border pieces, attach the border to the quilt at the corner, stitch it up and it will be perfect