For these DIY fabric coasters, all you need to start is a scrap of fabric with straight edges for the center of each coaster.
Find a scrap that is slightly longer than one straight edge of your first scrap and place it right sides together and sew in place along the raw edge with a 1/4″ seam allowance.
Use your regular piecing stitch length for this not the larger quilting stitch length. Then flip that scrap over so the right side is facing up and finger press along the seam.