make sure your oven is preheated before placing the fish in the oven. Bake for 12-14 minutes in the preheated oven. If you cook your fish longer it will be overcooked. When cooking halibut in parchment paper, you will know that it is done when it flakes easily.
We prefer to leave the skin on the sweet potato for the added fiber (even with skin included, this is still a low FODMAP food). If you prefer to chop and boil your potato to cook it, when you cook it you will create resistant starch. If you eat this cold, you will be eating resistant starch which will likely set off your symptoms. Always reheat potato (and rice) before eating. This breaks the bonds of the resistant starch.