Whisk the granulated sugar and salt in a bowl. Spread one-third of the mixture in an 8-by-8-inch dish. Place the salmon strips on top in one layer. Completely cover the strips with the remaining sugar-salt mixture. Refrigerate for 12 hours.
Preheat the oven to 170 degrees F. Remove the salmon strips from the curing mixture and carefully scrape off as much as possible. Blot dry all over with a paper towel. Arrange the salmon strips, spaced apart, on a rack set on a foil-lined baking sheet. Let the salmon air-dry at room temperature for 30 minutes.
Whisk together the maple syrup, brown sugar, soy sauce and liquid smoke in a bowl. Baste the salmon strips with the glaze and place in the oven. Continue to baste and turn the salmon strips every hour. In the last hour, don't glaze the salmon, but sprinkle the strips with the black pepper. Cook the salmon in the oven until the outside of the salmon is tacky to touch from the glaze but hardened, a total of 6 hours. It shouldn't be completely dry like jerky. Eat at room temperature and store in an airtight container in the refrigerator for up to a week.