Preheat oven to 400 degrees.
Place one crust into bottom of pie plate, gently working it down so no air pockets are left.
In a pan, warm apple juice concentrate on low.
In a small bowl, combine corn starch, cinnamon and salt, mixing well.
When juice starts to steam, whisk in corn starch mixture. Increase heat to medium, whisking constantly until bubbly. Add apple slices and fold into sauce to heat through. Remove from heat and allow to cool (at least 30 minutes).
Pour the filling into the plate.
Brush a little water onto the exposed edge of the bottom crust and lay the top crust over the plate. Gently press the two crusts together on the edge and pinch to seal. Sprinkle a little water and then sugar on top of the pie and cut small slits into the upper crust to allow steam to escape as it bakes.
Place pie on cookie sheet (in case filling overflows) and bake for 10 minutes.
Reduce oven temperature to 350 degrees (without opening the oven door) and continue baking for 40-50 minutes, or until filling is bubbly and crust is golden brown.