Prep the apples. Slice no more than 2 cm (½ inch) thick. Set aside in a large bowl or pot with in water with some lemon juice or ascorbic acid in it to prevent discolouring.
In a large pot, mix together the Clearjel, sugar, cinnamon, nutmeg if using, water and apple juice. Set aside.
Boil a large pot of water (4 litres / quarts). Add about 500 g / 4 cups of apples at a time to the boiling water. When the water returns to the boil after adding the apples, time 1 minute, then remove the apples with a slotted spoon or strainer, and put in a bowl or pot and cover to keep warm.
Repeat for all apples.
Put the apple juice mixture pot on to cook over medium high-heat.
When it starts to thicken, which will be very soon, add the lemon juice.
Cook for 1 minute, then remove from heat.
Stir in the apple.
Ladle apple into prepared half-litre (1 US pint) or 1 litre (1 US quart) jars
Leave 3 cm ( 1 inch) headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Process in a water bath or steam canner.
Process either size jar for 25 minutes; increase time as needed for your altitude.