Combine the flax chia blend with 1/3 cup water and let sit for 3 minutes.

Place the brown rice flour, oats, cornstarch, and 3/4 teaspoon salt in a food processor and pulse several times to combine.

Add the butter and pulse until the mixture resembles coarse crumbs with a few larger pieces of butter. Add the flax chia mixture and process until the mixture forms a dough, adding water as needed, 1 tablespoon at a time.

Roll the dough between 2 pieces of parchment paper into a ¼-inch thick circle. Place the rolled out dough, along with the parchment paper, onto a baking sheet and refrigerate for 30 minutes.

Cut the zucchini into 1/8-inch thick rounds. Place in a colander with 2 teaspoons salt, mix, and let sit for 30 minutes.

Preheat the oven to 400 degrees.

Place the zucchini slices on a clean kitchen towel and pat as dry as possible. Remove the tart crust from the refrigerator, remove and discard the top sheet of parchment paper, and spread the cheese evenly over the crust, leaving a ¼-inch border all around.