Butterfly and season the fish
Open the cleaned fish flat by cutting along the backbone and spreading it open while keeping the skin attached. Remove any remaining bloodline or unwanted parts, then pat the fish completely dry. Rub the flesh with salt, turmeric, coriander, black pepper, and olive oil. Allow the fish to rest while preparing the coating.
Butterflying increases the surface area exposed to heat, allowing the smoke and seasoning to reach more of the fish. Drying the surface improves flavour concentration and prevents steaming instead of roasting.
The fish should lie flat with the flesh exposed evenly. The surface should feel dry rather than wet or slippery.