I watched a demo a few years ago on making this exploding block. She took the top square, set a ruler from one corner to the opposite corner and and made three short cuts with the rotary cutter. Then she put the ruler on the other corners and made just two cuts, so that the cuts did not intersect with the first cuts. Now, after the top square is sewn on RST, it's super easy to get the scissors into those cuts and finish them into the corners. No drawing lines and trying to get the scissors into the fabric.