Prepare a grill for medium heat. Using a chef’s knife, cleaver, or serrated knife, cut fish crosswise into 2″–4″-wide planks (the larger the fish, the wider the planks); halve planks if fish is large. Pat fish dry, rub all over with oil, and season with salt and Aleppo-style pepper. Grill fish, undisturbed, until about 70 percent cooked through (use a knife to slide into flesh to check), about 5 minutes. The skin should release easily from the grate when the fish is ready to turn. If it’s sticking, keep cooking.