In a medium bowl, combine the flour, coconut oil, coconut sugar, and salt. Use a flexible spatula to combine the ingredients, mashing the contents thoroughly until a uniform dough forms.
Transfer the dough to a floured silicone baking mat. Flour the top of the dough and the rolling pin and begin rolling out the crust into a circle about 12 inches (30 cm) wide. If you do not have a silicone baking mat or other flexible surface, you can roll out the dough between two sheets of plastic wrap.
Roll the baking mat and crust onto the rolling pin and transfer to a 10-inch (25-cm) tart pan. Unroll the baking mat over the pan, crust side down, and peel off the baking mat. If the dough is sticking to the baking mat, transfer the baking mat and dough to the fridge for a few minutes, then try transferring the dough to the tart pan again.
Press the crust against the bottom and sides of the tart pan. Roll the rolling pin across the top of the tart pan to cut off any excess dough.
Refrigerate the crust for about 20 minutes while you prepare the filling, until the dough has firmed.
Preheat the oven to 400°F (200°C).
In a medium bowl, combine the coconut oil, coconut sugar, almond flour, arrowroot, cinnamon, and vanilla with an electric hand mixer. Pour in the milk and continue mixing until the filling is thick and well-mixed.
Transfer the chilled tart crust to a baking sheet. Pour the filling into the crust and smooth into an even layer with a spatula.
Arrange the peach slices over the filling in concentric circles.
Bake for 25-30 minutes, until the crust begins to darken and the peaches start to dry out.
Let the tart cool for at least 1 hour before unmolding.