Flour: I removed the squid from the marinade and dried with a paper towel. I made a mixture of AP flour, potato starch or "Katakuri-ko", and rice flour (about 1:1:1 ratio) or you could use just potato flour. This was my effort to try and maximize the crunchiness of the crust.
I shallow fried them in 170-180C oil (about half inch deep) turning often for 1-2 minutes. Because the oil tends to splatter, I erected a foldable metal wall around the pan. If I am not mistaken, this one was imported from Japan (even painted with a nice floral pattern, which is rather useless since the heat from the flame scorched the bottom black). We bought it at the hardware store specialized in Japanese items called "Soko hardware" 桑港金物店 in San Francisco Japan town many years ago. Sometimes, this works better than a Western-style splatter guard or screen. In any case, it may splatter a bit, so be careful. After I drained the excess oil on a paper towel, I served it with wedges of lemon while it was hot.
We had this with cold sake and it was a perfect starter dish. I made something else from the body of the squid.