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Gunkan or « Mothership » in Japanese is a typically Japanese way of serving ingredients which would be difficult to serve on top of a nigiri.
They are usually made by wrapping a piece of « nori »/dry seaweed around a ball of rice/shari with plenty of space left on top to fill.
Some people do not appreciate the « nori », but it could be replaced with very thin strips of daikon, cucumber, zucchuni and so on.
I hope to introduce more in the near future!