Measure the seat of the stool, and transfer this circle measurement to paper to make a pattern. Make the circle 1 inch larger for the seam allowance, and cut it out with the scissors.
Fold the fabric so that the wrong sides are facing out. Place the fabric onto a flat work surface.
Pin the paper pattern to the fabric. Cut out two fabric pieces for the stool cushion.
Measure the perimeter of the fabric circles you cut out in Step 3, and add 1 inch to this measurement. Cut a length of fabric that is this measurement long and 2 inches wide.
Fold the length of fabric in half lengthwise with right sides facing out, matching the long edges together. Sew 1/2 inch from the long edge along the entire length of the fabric.
Thread the cording through the fabric tube sewn in Step 5.
Adjust the fabric tube and the cording so that the cording is nestled right up along the folded edge of fabric. Carefully sew all along the other edge of the length of cording to keep the cording in place along the fold of the fabric tube.
Place one fabric circle on your work surface with the right side facing up.
Pin the fabric cording tube to the outer edge of the fabric circle, matching raw edges. Overlap the short edges.
Sew the fabric cording tube to the fabric circle 1/2 inch away from the raw edges.
Place the second fabric circle on top of the first fabric circle, with the wrong sides of the fabric circles facing each other. The fabric cording tube will be sandwiched in between the two fabric circles.
Sew around the perimeter of the fabric circles again 1/2 inch from the raw edges. Leave approximately 3 inches open for turning and stuffing the cushion.
Turn the cushion to the right side out.
Insert the batting into the cushion through the opening left along the side. Stuff the cushion until it is your desired firmness.
Hand-stitch the cushion opening closed with small whip stitches. Knot and clip the excess thread to finish the stool cushion.