If you'd like to try it yourself, here's the recipe. Just follow the instructions according to the smoker you are using.
1 cup brown sugar
1 cup kosher salt
1/3 cup soy sauce
5 1/3 cups water
2 pounds salmon
Mix first four ingredients. Add salmon; make sure it’s submerged in liquid.
Marinate 6 to 8 hours. Smoke until dry.
If using stovetop smoker, ½ hour on stove top, then 1 hour in oven at 250º.