Clean the fish, then either cut it up into portions or better yet leave whole if circumstances allow. This is awesome tilted next to an open campfire to cook, basting continuously.
Close the lid and try not to open it too often, but baste it first with whatever sauce your using. Be patient. This one is not done in a snap! Keep a spray bottle handy to spritz the wood with.
This will be a slow process. Get a book and read next to the bbq, making sure the boards don't go up in flames. Baste about every 20 minutes. Reposition the boards periodically for even cooking.
To use the campfire method, tap finishing nails around the perimeter of the salmon into the board. After that, secure the salmon with wire, weaving a zig zag pattern to fix in place.