Preheat oven to 450°
Bring crust to room temperature. Slowly and gently unroll one pie crust.
Carefully slide crust into a 9-inch pie plate. Trim bottom crust along edge of pie plate.
Combine the sugar, salt and flour. Sprinkle 1/4 of it over bottom crust in pie plate.
Heap rhubarb over this mixture. Sprinkle with remaining sugar and flour. Dot with small pieces of butter.
Slowly and gently unroll second pie crust, cut out decorative shapes with a small cookie cutter.
Place second pie crust over filling, wrap excess top crust under bottom crust edge, press edges together to seal, flute.
(Cover edges of pie with strips of aluminum foil to prevent excess browning.)
Place pie on baking sheet, carefully place pie on lowest rack in oven. Bake for 10 minutes. Reduce oven temperature to 375° and continue baking for 50 to 60 minutes. (Remove aluminium foil during last 15 minutes of baking.)
Serve warm with whipped topping or vanilla ice cream