Prepare pie crust if using homemade. Preheat the oven to 420°F (210°C).
Prepare the filling: If you're using canned peaches, drain the slices thoroughly and toss with flour, sugar, vanilla extract and milk.
If you're using fresh peaches, you will need to peel and slice them first. To do this, simply cut an “x” on the blossom end of the peach (the tip of the fruit opposite the stem side) and dunk each peach into boiling water for 30 to 60 seconds before dunking into an ice bath. The skins should peel off easily if the peaches are ripe enough.
Transfer the peach filling into the prepared bottom layer of the crust.
Make the lattice crust: Roll out the second disc of pie crust dough on floured surface until you get a 12″ circle. Using a pizza cutter, slice dough into ½″ pieces and start placing on top of pie dish, creating lattice design; tuck or pinch dough together for crust edge. Alternatively you could place entire piece of dough over top of dish, trim edge and crimp together and cut 1″ slits in the top to release steam.
Brush the top of the dough with melted coconut oil and sprinkle with coarse sugar and ground cinnamon if desired.
Bake at 420°F (210°C) for about 15 to 20 minutes, then lower the oven temperature to 350°F (175°C) and bake for 40 to 45 minutes until golden brown. You may need to turn your pie in the oven to get an evening browning.
Remove the pie from the oven and allow it to cool completely – about 3 to 4 hours.
Covered with plastic wrap, this pie can last in the fridge for up to 5 days, and up to 8 months in the freezer (see notes above for more information on storing and freezing).