I have made a very similar pattern, but there are no written instructions for mine. I can try and show you the first cuts of my strata and that might help.
Basically you stagger them by an inch or so and at the same time you alternate between cutting the wedge right side up then upside down. I've got to find the photos, so this will take a bit.
Very frustrating, but the only photo I can find is of the finished quilt. Grrrrr.... I will keep looking, because I had blogged about this and I know I had step by step photos.
Here's the end result of mine:
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