you still make rows, you just make them diagonally across the quilt....start with a bottom corner block and sew its sashing to it on both sides, then continue across, pinning careful at the top and bottom of your pre-cut sashing pieces. Then there will be a triangle needed at each end of each row and i put these on AFTER the rest of the row is sewn....now you can see what you need to make the triangle and each of these end triangles should have the straight of grain on the OUTSIDE edges for this application. so the easiest way to get it there is to cut a square with the bias (in the center of the square) that measures the same as the outside of your square... in this case 8".... (the top and bottom sash is not there yet)... this will make the triangle square (our edge pc) approx 5.6...so i would cut 5.75, sew on and trim later.... the bias side will be sewn to the first and last sash pcs on each end, so that is why its best to make the right size square and then cut diagonally...you will have both ends that way....
now the next cross row will be "sash, cornerstone, sash, cornerstone, sash".....all the way across....OR.... if you want to put your top row of sashing and cornerstones on before the first setting triangle...then sew them on first, now you have a square of 9.5 which makes your setting triangle 6.5 (to get a 9.5 bias) and then again, cut diagonally and put one on each end... sounds harder than it is.... you just want a square that gives you a long enough bias center cut to fit the side of your sashing...