Over season the flank steak with salt.
Blast sear it at 600 to 700°F, sear each side for 1 minute and then remove the flank steak form the grill and transfer it to a tray where you can wash the flank with Japanese Whisky. This is going to wash a bit of the salt off and begin to bulk up the flavor profile.
After 5 minutes in the whisky bath, carefully grab the steak with your tongs and transfer it back to the hottest portion of the grill. Do not transfer it near the grill with the whisky bath as the bath could easily catch flame. Grill the steak for another minute on each side.
As the whiskey crust forms and the alcohol evaporates you will find the flavor profile change with more complex depth. Look forward to fruity floral notes throughout, with honey, orange peel and white chocolate flavors depending on the whisky.
Transfer the steak from the grill to another tray and wash it with Japanese Soy. Soak for 1 minute, continuously rolling it in the soy sauce. Transfer the steak back to the grill for a third and final time. Blast sear each side for 1 minute to produce a thicker crust and bold umami flavors.
Let rest for 10 minutes, then slice once length wise and the rest ¼ of an inch thick across the grain.