Preheat the oven to 375°F. Place the minced garlic, pure maple syrup, soy sauce, and Dijon mustard in a small bowl. Whisk thoroughly until the ingredients form a smooth, uniform glaze. Allow the mixture to stand while preparing the salmon.
Pat the salmon fillets thoroughly dry with paper towels, then arrange them skin-side down on a baking sheet. Brush approximately one-third of the maple glaze evenly across the tops of the fillets, allowing a small amount to collect on the surface. Drying the salmon first helps the glaze cling to the fish and develop a glossy finish during baking.
Transfer the salmon to the preheated oven and bake for 10 minutes. Remove the baking sheet from the oven and coat each fillet with another one-third of the glaze. Return the salmon to the oven and bake for an additional 5–10 minutes, or until the flesh is opaque throughout and separates easily when tested with a fork. Layering the glaze during baking allows the coating to set gradually and intensifies its flavor without allowing the sugars to burn.
Remove the cooked salmon from the oven and immediately brush the remaining one-third of the maple glaze over the hot fillets. Leave the salmon to rest for 2 minutes before serving. The residual heat helps the final glaze settle into a smooth, lustrous coating without exposing the maple syrup to additional direct heat.