How to put a flat piping around a square with a mitered border

1: Mark 1/4" in from both sides on the border wedge. Place a piece of flat piping along the edge of the square and mark 1/4" in from both sides of the corner.

2: Align the 1/4" intersections then stitch the seam, stopping stitching at the 1/4" marks. Press the piping and the border away from the square. 

3: Mark 1/4" in from both sides on the other border wedge. Place a piece of flat piping along the edge of the square and mark 1/4" in from both sides of the corner.

4: Align the intersections.

5: If you stitch along the seam from the intersection, you will catch the seam allowance from the other side in the stitching. 

6: Make sure that the other border AND piping is folded out of the way BEFORE stitching the second seam.

7: Press the piping and the border away from the square. The corner of the square is free and will sit flat if you want it to!

8: Fold the border wedges right sides together and pin. The square will fold on the diagonal.

9: The view from the other side!

10: Stitch from the 1/4" intersections along the seam.

11: Press the seam open. 

12: Finished corner!