Rinse and cook rice according to the package.

While the rice is cooking, prepare the sushi vinegar. In a small saucepan, over medium-low heat, whisk together the rice vinegar, sugar, and kosher salt and heat until the sugar and salt have dissolved. Pour over the cooked rice and fan with a rice paddle to evenly coat the rice.

Line an 8-by-8-inch baking pan with a piece of plastic wrap. Gently and evenly press the rice into the pan then cover with another piece of plastic wrap. The goal is an even layer that is bound together but not squished and mushy. Place the pan in the freezer for 3 hours to firm up.

While the rice is chilling, make the spicy salmon mixture. Chop the salmon into small, ¼-inch cubes and place them in a bowl. Mix the salmon with the mayo, sriracha, soy sauce, 1 teaspoon toasted sesame oil, and green onion, and toss until well combined. Cover the bowl with plastic wrap and refrigerate until ready to use.

Once the rice has firmed up enough to slice easily, cut into 18 rectangles, 6 columns by 3 rows.

Set a wide-rimmed pan or pot over medium heat and fill with oil until about ½-inch depth. When hot, in three or more batches, fry the rice blocks until golden brown and crispy, about 1 to 2 minutes on each side. If the rice is browning too quickly, reduce the heat. Use a spider or a slotted spoon to remove the rice blocks and place them on a paper towel-lined plate to cool.

Once the rice has cooled to room temperature, top each block with a slice of avocado, a spoonful of spicy salmon, a jalapeño slice, a drizzle of toasted sesame oil, a drizzle of sweet chili sauce, and some toasted sesame seeds. Serve immediately.