Preheat the oven to 350 degrees F (177 degrees C). Line the bottom of a 9 in (23 cm) round pie pan with parchment paper, or grease well.

In a large bowl, mix together the almond flour, erythritol (if using), and sea salt.

Stir in the melted ghee and egg, until well combined. (If using vanilla, stir that into the melted ghee before adding to the dry ingredients.) The "dough" will be dry and crumbly. Just keep mixing, pressing and stirring, until it's uniform and there is no almond flour powder left. (Alternatively, you can use a food processor to mix it all together.)

Press the dough into the bottom of the prepared pan. You can flute the edges of desired; if it crumbles when doing this, just press it back together. Carefully poke holes in the surface using a fork to prevent bubbling.

Bake for 10-12 minutes, until lightly golden. (Add fillings only after pre-baking.)