In a medium mixing bowl, whisk together the finely ground almond flour, erythritol (if using), and salt.
Add the cold, cubed butter. Use a pastry blender or your fingertips to cut the butter into the flour mixture until it resembles coarse, sandy crumbs.
Drizzle in 1 tablespoon (15 ml / 0.5 fl oz) of cold water and mix until the dough starts to come together. If it's still too dry, add the second tablespoon. Gently form the dough into a disc.
Wrap the dough disc tightly in plastic wrap and refrigerate for at least 30 minutes to firm up.
Preheat your oven to 350°F / 175°C. Lightly grease a 9-inch pie plate.
Unwrap the chilled dough and press it evenly into the bottom and up the sides of the prepared pie plate. If the dough sticks to your fingers, dampen them slightly with water.
Use a fork to prick the bottom of the crust a few times. This prevents it from puffing up during baking.
Bake for 12 to 15 minutes, or until the edges are lightly golden brown.
Let the crust cool completely on a wire rack before adding your filling.
