ok I made the block using a 10" pre-cut the finished block is 11.5 x 11.5 the cuts on the 10" block was at 2.5 inches
you sew 2 10 inch squares right sides together, using 1/4" seam, Sewing 2" from the top right edge, pivot 1/4" from the corner and sew to the bottom left edge, sewing 2" from the left edge,sew to the top left corner, pivot 1/4" sew to starting point, top right edge.
cut the unit diagonally through the sewn corners, stack the triangles, carefully aligning all edges,make sure you place the cut triangles together as shown in the diagram. Measure 2.5" from the left edge and cut through all layers, Without disturbing the stack, measure 2.5" from the bottom edge and cut through all layers. Iron, arrange the units as shown, sew and trim to 11.5"
Edited by katsdar - 5/30/16 at 9:01pm