Prepare grill/smoker for indirect heat at 225 degrees.
Make rub by coarsely grinding the spices. Use a mortar and pestle, coffee/spice grinder, or just crack on a hard surface with a blunt object
Let trout reach room temperature. Brush with olive oil and then rub dry spice mix all over the fish.
Place fish skin side down in the smoker on an oil sprayed seafood pan. Alternatively use an oiled napkin and wipe on the grill grates to avoid the fish skin sticking.
Smoke for 1 1/2 to 2 hours. Check the internal temperature after an hour. 125 degrees is ideal for you to remove from the grill/smoker. This will help you avoid drying the fish out and as you allow it to rest the fish will eventually reach FDA level (140-145 degrees) doneness.
Salmon is a perfectly suitable alternative to trout.
Let the trout reach room temperature before cooking
Use a mortar and pestle to crush the spices. Otherwise using a hard surface pound them lightly with the blunt side of a hard object.
Buy quality fish! Not even a killer spice rub and big smoke can save bad ingredients
Use a grill pan for the fish and spray with oil beforehand. Grill pan helps to ensure the fish stays intact. If you don’t have a grill basket/fish pan use a big spatula.
Make sure your grates are clean before cooking the fish
This dish works well grilled too if you don’t have the time or want less smokiness. See Cedar Plank Grilled Trout recipe for a grilled example which is more of a high heat recipe.