Prepare the apple juice: Add the apple scraps and water to a large pot. Bring to a gentle boil, then lower to a simmer for about 30 minutes. Mash the scraps lightly to release extra juice and flavour. Strain through cheesecloth or a fine sieve without pressing. Measure out 6 cups of strained juice.
Sweeten and spice the juice: Pour the juice back into the pot and add the sugar, lemon juice, and cinnamon sticks. Warm over medium heat until the sugar fully dissolves.
Add the pectin: Remove the cinnamon sticks. Stir in the pectin and turn the heat to high. Bring to a full rolling boil that cannot be stirred down. Boil hard for 1 full minute, stirring constantly.
Check for set: Remove from heat and skim any foam. Drop a small amount onto a cold plate and check for slight wrinkling when pushed — a sign it’s ready.
Jar the jelly: Ladle the hot jelly into prepared jars, leaving ¼-inch headspace. Wipe rims and apply lids. Process in a boiling water bath for 10 minutes. Allow jars to cool undisturbed for 12–24 hours.