Perhaps cut a rectangle with the longer side an inch (or more) longer than your square and cut once diagonally. Sew to opposite sides of the square (with the diag. cut side to the outside). Trim off the excess. Measure the remaining 2 sides and repeat. Trim off excess to square up. I assume the longer the rectangles the wider the 'border' will be.
Last edited by Gay; 06-10-2020 at 04:23 PM.