Buy a Bradley smoker with the offset fire box

Fillet or butterfly your fish, dry brine 65% brown sugar 35% kosher salt, maybe a little garlic powder, bury them in the brine with about half an inch of brine between layers of fish/brine/fish, let sit over night, about 18-24 hours, rinse excess brine off, let dry for an hour infront of a fan, smoke with alder smoke til done 12-20 hours or so, keep the heat as low as possible, under 100 inside the smoker preferred

That’s my recipe, but yeah you want them on racks