01 - Set oven temperature to 400°F and allow it to fully preheat.
02 - Fit the unbaked 9-inch pie crust into a pie pan, carefully crimping the edges for a secure and attractive finish.
03 - Pour 1 1/2 cups water directly into the prepared pie crust.
04 - Mix granulated sugar and all-purpose flour together in a mixing bowl until completely blended. Evenly scatter over the water within the crust.
05 - Drizzle vanilla extract over the surface, sprinkle with a pinch of salt, and disperse thin pats of unsalted butter uniformly over the top.
06 - Place the pie on the lower oven rack and bake at 400°F for 30 minutes.
07 - Reduce oven temperature to 375°F. Continue baking for 20 minutes, until the crust is golden and the filling is set but still slightly jiggly at the center.
08 - Remove from oven and allow pie to come to room temperature. Refrigerate for at least 2 hours before slicing to achieve optimal texture.