Shiokara is very simple to make. I find that every time I make a batch it doesn't last very long, as I find it very addictive! And definitely homemade is the way to go. Until I had my first chance to try a homemade shiokara I swore the stuff was as awful tasting as it's typical English translation sounds.
Invariably on menus, product labels, "weird foods" websites and on "Fear Factor" it's described as "fermented squid with the guts". I'll have to admit that it's an accurate name, but not very marketing-friendly nor indicative of the wonderful taste that one should expect. I'd rather think of it as prepared squid with it's liver. True it's a fermented product, but to some squid is scary enough to almost not consider having without ruining the deal by adding the "f" word.
And guts? Well I don't know what's what in squid anatomy, but my guess is that by looks and taste that most of the "guts" of the squid by volume comes from this one huge sac-like structure that I'm guessing is the liver. Surely that's what it tastes like to me, and liver is the predominant taste in the shiokara.
Here's how my Mom taught me to make it. It's very simple.
Just take a fresh whole squid, available locally at Mitsuwa or Nijiya, and carefully remove the head. Pull out the ?quill?, a plastic-like structure that runs the length of the squid. Also remove the beak where the legs come together.
Carefully without bursting it remove the aforementioned sac-like structure, which I assume is the liver. Now remove the skin-like outer membrane that covers the entire outside of the squid. This part can be a little tricky and time-consuming. I'll often do this under running water and use my fingernails to start a small tear in the membrane and then with my fingers try to peel a larger section off. I've heard that the trick is to start at the tip of the head end and peel down, but your mileage may vary! (The latter was advice from a sushi chef...)
Cut up the now skinned flesh into short noodle-like sections, including the tentacles. To this squeeze the contents of the removed sac, and to which I add sea salt, some shichimi/togarashi/or red pepper of your choice, and citrus zest. (Yuzu would be great if you can find it, but lemon works quite well...)
Mix it up and keep refrigerated in a sealed container. I find that it can be eaten immediately after throwing it together, (I taste the shiokara as I'm seasoning it...), but improves in taste after a stint in the refrigerator.