Rub the salt on the whole surface of a salmon fillet. Let it rest for 30 minutes. Preheat the broiler with high setting. Place the fillet on a rack with a baking pan. Position the salmon skin side down about 6 inches from the heat source and broil for about 10-12 minutes. Flip the fillet to crisp up the skin. When it cools enough to handle, flake the salmon. Sprinkle salt to season. Salmon flakes should be seasoned enough.
Make a scrambled egg. Mix eggs, mirin, and kosher salt in a bowl. Heat canola oil in a pan, pour the egg mixture. As the bottom of egg mixture starts firming up, stir with chopsticks. Once the egg is fully cooked and scrambled, remove from the heat and set aside.
Mix sliced cucumber and kosher salt. Let it rest for a few minutes. Squeeze water out of cucumber.
Mix sushi rice with toppings, scrambled egg, toasted sesame seeds, cucumber, flaked salmon. Serve it on the platter topped with ikura and shredded shiso leaves.