From The Big Green Egg® Cookbook.
Set the EGG for direct cooking.
Preheat the EGG to 400°F/204°C.
Place the cedar planks in a pan, cover with water, and let soak for 1 hour.
Whisk the mustard, honey, balsamic vinegar, orange zest, and 1 teaspoon thyme together in a small bowl.
Place the cedar planks on the grid, close the lid of the EGG, and preheat for 3 minutes. Open the lid and turn the planks over, brush them with the olive oil, and place 2 salmon fillets on each plank. Season the salmon with salt and pepper and brush generously with the honey glaze. Close the lid of the EGG. Cook the salmon for 12 to 15 minutes for medium.
Remove from the heat, garnish with thyme, and serve immediately.