This is how I do it. Use salmon that has been frozen for a minimum of 7 days below 0°F. This will kill some parasites that could be in the fish. In a shallow, non-reactive pan layer about 1/4" of kosher salt, then place the now thawed salmon skin-side down on the salt. Roughly chop a handful of fresh dill and spread over the top of the salmon, use as much as you'd like. You could add other spices now, I don't. Finally pour more kosher salt on top of the dill and fillet until it's completely covered. Cover the container and refrigerate it for at least 12 hours, more won't hurt. when the time is up wash the fillet under cold, running water. some of the dill may remain, but all the salt will wash off. the fillet will become somewhat firm during the process. Now soak the fillet in fresh cold water for 2 or 3 hours changing the water a couple times to draw some of the salt back out. You can taste the salmon now to see if you like the salt level or need to soak it a bit longer if you're so inclined. Once its how you like it, place the fillet on a rack uncovered so air can circulate around it, and let it dry out in the fridge for another 12 hours or so (I have done less in a pinch). The color will darken a little, and take on a shiny look. The fillet will be dry to the touch, and it's ready to smoke (or eat immediately as gravlax).
I like the outside temp to be in the low 30°s when I make this. My smoke comes from and Amaze-N-Tube smoker and burns for about 6 hours adding little heat to the cabinet. once the smoke process is done I zip-lock the fish, and leave it mellow in the fridge for a week or so. It's then ready to eat, or vacuum pack and freeze for later use.
Obviously employ any additional food safety precautions you deem necessary.
