Soak the cedar planks in water for at least two hours. Pat the planks dry and rub the top with 1 TBS olive oil per plank. Rinse the salmon, pat dry and place, skin side down on the cedar plank. Liberally rub each plank with potlatch seasoning. Remove the fennel fronds and place over the salmon. Grill using indirect heat or smoke until the fish is firm to the touch but not dry.