Originally Posted by Prism99

You don't have to use cornerstones to get sashing to line up.

I put the quilt together in rows first, with the short sashing strips in-between the blocks. Sew the long sashing strip to the bottom of the first row. The important step at this point is to turn the row-with-long-sashing-strip to the wrong side. Use a ruler and pencil to extend the seam lines from the row of blocks down through the long sashing strip. When you attach the second row to the long sashing strip, use pins to match up the marks on the sashing strip with the seam lines in the second row. Use the same technique after adding a long sashing strip. This keeps all the blocks lined up.

The pencil marks on the wrong side of the long sashing become "virtual" seamlines. This is a lot faster than adding cornerstones, as there is a lot less cutting and sewing. The only extra step is drawing the pencil marks on the wrong side.