Preheat oven to 450º F.
Turn both pie crusts out on a lightly floured surface and stack one on top of the other. Roll them out to roughly a 12×17-inch rectangle, then transfer crust to a large baking sheet (10×15-inches).
Tuck any excess crust under itself, then crimp edges as desired, pricking the bottom and sides all over with a fork.
Place baking sheet in oven and bake for 9-11 minutes, or until golden brown, then remove from oven and let cool.
In a large saucepan over medium heat, whisk together jello packet, sugar and cornstarch, then pour in sprite and lemon juice.
Bring mixture to a boil, stirring until thickened, then remove from heat and let cool 10-15 minutes.
Once crust has cooled, arrange sliced strawberries on top, then pour (cooled) filling carefully on top.
Refrigerate slab pie for 2+ hours, or until set, then slice, serve and enjoy.
