I use cauliflower rice. Cook it in a pan with some butter for about 5 mins (just to soften it a bit). Season - obviously! I have also been known to add crushed garlic to it. Cook the fish in a little butter (just to flake level).
Let it cool, then flake the fish, mix with cauliflower rice, and then I add lemon zest, parsley, and chopped spring onion. Form into patties.
I vary at this point. Sometimes, I dip the patties in egg, then coat in my crumb mix of almond flour, milled flax, and parmesan. Other times, I just add it to the mix. If you are going to "crumb" them, the patties will need a chill in the fridge. They freeze well too.