Preheat oven to 400°F.
Place pie crust on a baking sheet and pour the 1 1/2 cups water into the pie crust.
In a small bowl, whisk together the flour, sugar, and salt. Sprinkle evenly over water in the pie crust, but do not stir.
Drizzle vanilla over the pie, then evenly place pats of butter over the top.
Bake for 30 minutes. Reduce heat to 375°F and continue baking for 30 more minutes. Cover crust with foil if browning too quickly.
Pie will be watery but will set up as it cools. Allow to cool to room temperature, then place in fridge to chill before slicing. Enjoy!
