In a mixing bowl, combine the granulated sugar, kosher salt, coarsely ground multi-color peppercorns, liquid smoke, fresh dill, and chili pepper flakes (if using). Mix well until all ingredients are evenly distributed.
Rinse the salmon fillet under cold water and pat it dry with paper towels. Place the fish on a cutting board, skin side down.
Generously coat the flesh side of the salmon with the curing mixture, making sure every inch is covered. Use your hands to press the mixture into the fish, ensuring it adheres well.
Wrap the salmon tightly in plastic wrap. Place it in a shallow dish or on a tray to catch any liquid that may drain during the curing process. Refrigerate for 48 to 72 hours, depending on how cured you want your lox to be.
After the curing time is complete, remove the salmon from the refrigerator. Unwrap and rinse the fillet under cold water to remove any excess curing mixture. Pat dry with paper towels. Using a sharp knife, slice the salmon thinly at a diagonal angle.
Your homemade lox is now ready to be enjoyed! Serve it on a toasted bagel with cream cheese, capers, and a sprinkle of fresh dill.
