Combine all of the dry brine ingredients. Spread one-third of the brine in the bottom of a large dish. Place the salmon on top of the brine, skin side down. Sprinkle the remaining brine on top of the salmon and gently press the brine to adhere. Cover with plastic wrap and refrigerate for 4 to 6 hours.
Soak your preferred wood chips in water for at least 30 minutes.
Prepare the barbecue for indirect cooking over medium heat (190°C to 230°C) with smoker box(es) if using a gas barbecue. Drain and add the wood chips to the charcoal or to the smoker box of a gas barbecue, following the manufacturer’s instructions.
Rinse the salmon under cold water and pat dry with paper towel. Drizzle the oil over both sides of the salmon and place onto a large sheet of baking paper.
Once the barbecue has preheated and when smoke appears, add the salmon to the barbecue, and roast over indirect medium heat, with the lid closed, until firm and slightly pink all the way to the centre, about 30 minutes.
Remove the salmon from the barbecue and allow to cool to room temperature. Refrigerate until required.
To make the lemon caper sour cream. Combine all of the lemon caper sour cream ingredients in a bowl. Season to taste.
Slice the baguettes into thin slices. Spray both sides of the bread with the olive oil spray.
Prepare the barbecue for direct cooking over medium heat (180°C to 230°C). Place the baguette slices onto the barbecue and grill for 1 minute per side.
Spread the lemon caper sour cream onto the baguette slices, top with the salmon and finish with a sprinkle of chives.