Wash the halibut and pat dry. Place the halibut on the baking sheet, lightly cover with almond flour and a few pinches of salt. Bake for 15 minutes or until the fish is tender and cooked through (no pink left).
While the halibut is baking, place 1 tablespoon of olive oil in a skillet on medium heat and sautee the mushrooms for 10 minutes or so, tossing occasionally. You can also add pinch of salt while tossing them.
In the last 5 minutes before the halibut it done, remove the mushrooms from the skillet and place the garlic in it on a low heat for a minute or so.
Add the spinach to the skillet with the garlic and sautee for a few minutes or until cooked.
Add the spinach, mushrooms, and halibut to a plate and serve with a slice of lemon.