Submerge the cedar planks in water for at least 4 hours. This will prevent the wood from catching on fire and burning.
In a small bowl, combine the 1 tsp salt, 1/2 tsp cumin, and 1/2 tsp chili powder.
Drizzle 3 tablespoons olive oil over the fillet. The grate the 3-4 garlic cloves using a zester or garlic press and spread the grated garlic over the oiled salmon.
Season the salmon with the seasoning mix and place on each cedar plank, skin side down.
Grill at 500 degrees Fahrenheit for 15-20 minutes. Grilling time may vary depending on the thickness of each fillet. You want to make sure the thickest part of the salmon reaches at least 145 degrees Fahrenheit. Use an instant-read thermometer to check the fish temperature.