Preheat the oven to 400°F (205°C). Position the unbaked pie crust on a sturdy baking sheet.

Carefully pour 1.5 cups of purified water into the pie crust.

In a separate mixing bowl, combine the all-purpose flour and granulated sugar. Ensure they are mixed thoroughly.

Evenly distribute the flour and sugar mixture over the water in the pie crust. It's important not to stir after this step.

Gently drizzle the vanilla extract over the ingredients in the pie crust.

Arrange the portions of unsalted butter uniformly atop the mixture.

Insert the pie into the preheated oven and bake at 400°F (205°C) for approximately 30 minutes.

After the initial baking period, reduce the oven's temperature to 375°F (190°C). Monitor the edges of the pie crust and shield them if they appear to be browning too rapidly. Continue baking for another 30 minutes.

Upon removal from the oven, the pie may exhibit a liquid consistency. This is expected. As the pie cools, it will solidify. Allow the pie to reach room temperature. Thereafter, for optimal texture, cover and refrigerate until thoroughly chilled before serving.