Remove the shell of the geoduck. Remove the skin and wash thoroughly. Slice geoduck into very thin slices. In a wok or large saucepan, heat water to 65°C /150°F. Add geoduck slices and blanch briefly. Transfer with slotted spoon to a large bowl of ice water, chill thoroughly and set aside until ready to use. Infuse olive oil with fresh sansho peppers to make sansho pepper oil. Cut coloured peppers into thin strips and season with salt. Add sansho pepper oil and toss to mix. Transfer to serving platter. Remove geoduck from ice water and drain well. Add a dash of Japanese soy sauce and heated sansho pepper oil and toss to mix. Transfer to serving platter. Garnish with sansho pepper and serve.