Peel, core and slice the apples about 1/4 inch (6 mm) thick. You should have about 7 to 8 cups. Toss with the lemon juice to stop browning.

In a large pot, whisk the sugar, cornstarch, cinnamon, nutmeg and salt, then whisk in the water or cider. Cook over medium heat, stirring, until thick and glossy, about 2 minutes.

Add the apples and stir to coat. Cook for 2 to 3 minutes, just until the slices start to soften at the edges but still hold their shape. Don't cook them through.

Spread on a tray and cool completely, first at room temperature, then in the fridge.

Line a 9-inch pie dish with a large sheet of plastic wrap or foil, leaving plenty hanging over the edges. Spoon in the cold filling and fold the wrap over the top.

Freeze until solid, about 4 hours. Lift the frozen disc out of the dish, wrap it again tightly, and seal it in a freezer bag. Label with the date. Freeze for up to 6 months.

To bake: line a pie dish with pastry, unwrap the frozen filling and set it straight into the crust. Add a top crust or crumble, cut vents, and bake from frozen at 425°F (220°C) for 20 minutes, then at 375°F (190°C) for 50 to 60 minutes more, until the juices bubble through the vents. Cover the edges with foil if they brown too fast.