Welcome to the board. I don't have the pattern for this but there are 2 ways to put it together, either as a square joining octagons, or making the large star into a square. Personally I would use B style, though you would still have to 'set-in' the squares on the corners - although they could be created using triangles and included while making the larger star.
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I really wished I had known about option B, which looks more sensible than the pattern. Thank you for your wonderful suggestion.