Rinse the squid thoroughly and pat dry. Cut any large tentacles in half lengthwise and the tubes into 1/2-inch rings.
Whisk the buttermilk, 1 1/2 teaspoons salt, and the hot sauce in a medium bowl. Drop the squid into the mixture and soak for 30 minutes.
Combine the flour, cornmeal, and cornstarch in a medium mixing bowl. Drain the squid from the buttermilk mixture using a mesh strainer then dredge the squid, in small handfuls, into the flour mixture, tossing with your fingers to prevent clumping. Place on a half sheet pan fitted with a wire rack and set aside while you heat the oil.
Place a 5-quart Dutch oven over medium-high heat until the temperature reaches 375℉. Set a wire rack over a paper towel lined half sheet pan and have standing nearby your cooktop.
Gently place small handfuls of dredged squid into the hot oil and fry for 1 minute. Remove from the oil with a spider or slotted spoon and place on the paper towel lined sheet pan. Season while hot with additional kosher salt and freshly ground black pepper. Repeat with the remaining squid. Serve immediately.