Cut two 18-inch squares in the fabric of your choice.
Draw a 12-inch square in the center of each piece with a piece of chalk.
Cut a slit every inch around the perimeter of the fabric, extending straight in from the edge of the fabric to the chalk line. This will create a border of inch-wide strips around each piece of fabric.
Place the two pieces of fabric on top of each other, good sides out.
Tie a strip from the top piece together with a corresponding strip from the bottom piece, knotting them securely together.
Continue knotting strips together around three sides of the pillow.
Stuff the pillow with cotton or polyester batting. The amount used depends on how firm you want the pillow to be. Use more for a firmer pillow, and less for a more squishy one.
Knot the strips on the final side of the pillow.