The first point is that you will need to make the borders longer than just the width of the quilt or panel. The panel shown is 10.1/2" wide and the border is 2.1/2" so I have cut the border strip 14.1/2" long. That's 10" for the quilt block and 2" extra each side. Find the middle of both the border and quilt block (by folding in half) and pin the border in place.
With right sides together and using a 1/4" seam, sew the border to the top of the quilt block. Begin sewing 1/4" from the edge of the quilt block (on the left) and finish sewing 1/4" from the edge of the quilt block (on the right).
Repeat the procedure with a strip of quilt border down the next edge of the quilt block (or quilt), again beginning and ending the stitching 1/4" from the edge.



