Wash, peel, and slice peaches into 1/2-inch thick pieces. (Blanch in boiling water for 30 seconds then ice water for easier peeling).

Combine peaches, sugar, and lemon juice in a large saucepan.

Stir in the liquid pectin.

Bring to a full rolling boil over high heat, stirring constantly. A full rolling boil is a boil that cannot be stirred down.

Boil hard for exactly 1 minute, stirring constantly.

Remove from heat, skim off foam, and ladle hot jam into sterilized half-pint jars, leaving 1/4-inch headspace.

Wipe jar rims, add lids and rings, and tighten fingertip tight. Process in a boiling water bath for 10 minutes (adjust for altitude) for longer shelf life, or refrigerate and use within 2-3 weeks.

Cool completely. Sealed jars will make a popping sound. Store sealed jars in a cool, dark, dry place.