Preheat the oven to 400 ºF and cover a pizza plate with parchment paper. You can also cut parchment paper to match the shape of the perforated pan.
In a medium bowl, add ground flaxseed and water and let stand until mixture thickens.
Place the cauliflower florets in the large bowl of the food processor with an "S" blade and operate until reduced to a rice texture. Pour the cauliflower "rice" into a large saucepan, add enough water to cover, and bring to a boil. Cover, reduce heat, and cook for 5 minutes. Drain the liquid, transfer the cooked cauliflower rice to a bowl, and leave to cool in the freezer for 10 minutes.
Remove the chilled cauliflower rice from the freezer, transfer it to a bag of nut milk, gauze or the center of a thin dish towel, and squeeze the rice with your hands, removing all the excess moisture from the cauliflower.
Place the drained cauliflower in a large bowl, then add the flax mixture, ground almonds, garlic, onion powder, and dried parsley.
Stir well to mix well, then squeeze the mixture into the baking sheet covered with parchment. Shape the crust into the desired size with a slanted spatula or your hands, keeping the crust about ¼-inch (8 mm) thick. For best results, press firmly on the crust, ensuring that there are no "thin spots," still remembering to make the center slightly thinner than the sides.
Place the crust in the oven. Bake for about 30-40 minutes until the top is lightly browned and dry to the touch.
To flip the whole pizza crust, preferably use an extra piece of parchment paper on top, then flip it into the baking sheet without the parchment paper to cook for an additional 15 minutes or until it is dry.
Add your favorite pizza toppings and return briefly to the oven to let it heat up about 5-10 minutes extra.