Mix all marinade ingredients together in a glass baking dish and marinate fish fillets, flipping halfway through, for about an hour.
Remove fish and reserve leftover marinade.
In a small bowl, mix starch with cold water into a smooth slurry consistency, making sure all lumps are gone.
Transfer leftover marinade into small saucepan and heat on medium low. Gradually mix in starch slurry and cook for 2-3 minutes stirring frequently while glaze thickens.
Preheat barbecue to medium heat then place fish directly on oiled grill or on piece of aluminum foil.
Brush maple soy glaze onto salmon fillets and cook for 12-15 minutes. Fish should just start to flake when poked with a fork and be slightly translucent in the middle when done.