BEAUTIFUL!!!!
I have never tried anything like that! but I sure could figure out how to!
it looks like it must be needle turned. the space between the blue is exactly the same width as two seam allowances. if you were to fold the fabric in four, or eight in this case then you could cut the pattern and then unfold, lay it back out, at this point the cuts could touch. pin or baste the thing down and then carefuly needle turn each strip.
that is how I see it being done and how I would attempt to do one myself.