I made lots of string quilts, a few QAYG. Where you cut backing and batting square using the sew and flip.
Easier I sewed three or four strips together,Lay another strip on top, sew both strips together each side. Lay triangle ruler on bottom of seam allowance, cut triangle flip ruler and cut from opposite seam allowance. Keep going across the strip. Sew four triangles together. Very easy.
There may be a tutorial on this site.