I agree with Prism about lining up the points before sewing together.
Another potential method I googled yesterday is the 3D Bow Tie block. It uses five 5" squares (1 white & 4 coloured), and is similar to the first method you used. I'm wondering if one used four 5" and one 9-9 1/2" white squares it should produce a simple CW block. Of course there would be an extra square for the 'glass', not sure what the size would be. I am going to have to experiment with this as a CW quilt is on my bucket list.
https://www.youtube.com/watch?v=BVdfuGgtHf8