well, of coarse it's easy. what is it? sliced raw fish made pretty on a plate. how hard can that be? so, i have no real secrets for ya, but i can tell you a real quick cheater way to have some dee-lish octopus sashimi at home and you can impress your friends with this as a starter or a side to a great meal.
so what's my big secret?...
1st. don't try to deal with this eight legged bugger and think you're going to cook it to proper sashimi texture yourself..unless your an octopologist of some sort.
2nd..."you're only as good as your tools"...in this case, i let my fingers do the walkin'. i googled all the Japanese markets in the area and chose the best one.
i found this beautiful octopus at Mitstuwa. funny thing is...i was on the hunt for chicken feet!!!...my octopus obsession was last month, hence the reasoning for my suggestion of not trying to cook this yourself. cleaning the thing alone, i mean with a BEAK and all, didn't sound fun, let alone the fact that i couldn't find a whole, fresh octopus anywhere. they were all frozen. then there's the fact that cooking it so that it's buttery tender enough for sashimi, might be a different cooking technique than just the normal instructions i found.
so long story short, go to a Japanese market and pick out a perfectly cooked octopus tentacled leg. i bought one that was a little less than 1/2 lb and it would have been great for 4-5 people to enjoy a few slices (kinda all you need for an app.). while you're there look at the dressings...good luck!...it's really hard to pick out something when you can't read the lable. instead i went to Bristol Farms and asked how they make thier yummy chili oil they use on thier spicy poki.
sesame oil, chili oil, cayenne, sea salt, seaweed, white and black sesame seeds and ground pepper. you could, of course just go traditional and serve with soy, ginger and wasabi.
so that's it...go and have fun investigating your local Japanese/Asian market. some of the stuff you'll find is definitely and eye-opening experience. i wouldn't do my shopping there, but i will go back for sushi grade goods.