About blind baking
The term blind-baking (sometimes called "pre-baking") refers to the process of baking a pie crust or other pastry without the filling.
Generally, the pie crust is lined with tin foil, greaseproof paper or 'reusable greaseproof paper' , then filled with dried peas, lentils, beans, rice or other pulses, or with ceramic "baking beans", so that it will keep its shape when baking. Metal or ceramic pie weights are also used. After the pie crust is done, the pulses are replaced with the proper filling. Blind-baking is necessary if the pie filling can not be baked as long as the crust requires, or if the filling of the pie would make the crust too soggy if added immediately.
Blind-baking is essential if the filling is not intended to be baked, for example a chilled filling.
As pictured, if there is any overlap, it's better to wait until the pastry has be blind-baked and trim it off then. This will prevent the sides from shrinking.