Wash, pit, and finely chop the peaches until you have 4 cups. Peeling is optional — the skins soften during cooking, but you can peel them for a smoother texture.

In a large jam pot, combine the chopped peaches, sugar, and lemon juice. Stir everything together over medium-high heat.

Bring the mixture to a full rolling boil, stirring constantly so it doesn't stick. The mixture should be bubbling across the entire surface.

If foam starts to appear, add a small knob of butter (about ½ teaspoon) to help reduce it.

Once boiling hard, quickly stir in the pouch of liquid pectin. Continue stirring and boil for exactly 1 minute.

Remove from heat and skim any remaining foam from the top if needed.

Ladle the hot jam into sterilized jars, leaving ¼ inch of headspace. Wipe rims clean and apply lids and bands.

Process the jars in a boiling water canner for 10 minutes, then remove and let cool undisturbed for 12–24 hours. Check seals before storing.

Once opened, refrigerate and use within 3 weeks. Unopened jars can be stored in a cool, dark place for up to 1 year.