1. Use a pencil to mark a diagonal line on wrong side of 42 assorted blue print 8" squares and 42 assorted green print 8" squares. (To prevent fabric from stretching as you draw the lines, place 220-grit sandpaper under each squares.) Set aside marked green print squares for Step 3.
2. Layer a marked blue print square atop an unmarked green print 8" square. Sew pair together with two seams, stitching 1/4" on each side of drawn line (Diagram 1). Cut pair apart on drawn line to make two triangle units. Press each triangle unit open, pressing seam toward green print, to make two triangle-squares total. Each triangle-square should be 7-5/8" square including seam allowances.
3. Repeat Step 2 using remaining marked blue and unmarked green print squares and unmarked blue and marked green print 8" squares to make 168 triangle-squares total.
4. Use a pencil to mark a diagonal line perpendicular to seam line on wrong side of 84 triangle-squares.
5. Layer a marked triangle-square atop an unmarked, nonmatching triangle-square, aligning seam lines. Sew pair together with two seams, stitching 1/4" on each side of drawn line (Diagram 2).
6. Cut pair apart on drawn line to make two triangle units. Press triangle units open, pressing seams in one direction, to make two hourglass blocks. Each hourglass block should be 7-1/4" square including seam allowances.
7. Repeat steps 5 and 6 using remaining marked and unmarked triangle-squares to make 168 hourglass blocks total.