ok I'm doing a rainbow trout but the proceedure the same.
First butterfly fish

then rub with brown sugar and sprinkle with cracked pepper and nail and wire it

place over hot coal( I used to use spilt wood but hard to keep coals that are not hot) I now use lump coal

make a "hut" and smoke, for salmon I start around 10 am and check peroidicly adding coal or smoke wood and rub more sugar on to make a thicker crust

my daughter checking on it lol

about 45 min before supper(for 4 to 5 pound fish) I crank up the heat and cook it

and the finished product

wild fish are better and my salmon planks are 2x10"s with a stake so when I do 4 I stick them and lean them in and to cook I stick them straight up next to a big fire. On bigger fish I put them head down, tails cook faster; sometimes the tail is done so i either cut it in the middle and eat the tail first while cooking the head or finish in the oven( smell of smoke will go thru the house)
Like I said the karate instructor always asks, well tells me I'm planking salmon right! lo and its the only way my wife will eat salmon!