This brine could not be simpler. After you mix the maple syrup, soy sauce, orange zest, and garlic together, your brine is done. Place your fish skin side up in a zip top bag, you can use a shallow baking dish, but the marinade doesn’t tend to cover the fish as evenly, the fish will sit on the bottom of the pan and the brine will not touch the flesh, and you need more marinade to do the same task. Let this sit overnight for maximum effect as the salt and sugar do their thing.
On the day of, you will notice that the flesh has firmed up and has taken on a darker color. This is the work of the brine and will help in the grilling process.