Fill an empty biscuit tin with 2 handfuls of incense flour. Place the fresh rosemary and sage sprigs on top. Insert a small grate or piece of wire mesh so it rests about halfway up the tin. Pierce the tin lid 5-6 times with a screwdriver.
Salt the salmon fillets and rub with olive oil. Place them skin-side down on the wire rack or mesh. Cover with the lid and place the tin on the stove or charcoal grill over medium heat. Cook for 8-10 min—smoke will rise through the lid holes.