Place peaches in a glass or plastic container with a lid and immediately mix with lemon juice to prevent browning. Stir in sugar and ginger. Cover and marinate in a cool place, 8 hours to overnight.

Inspect 5 half-pint jars for cracks and rings for rust, discarding any defective ones. Immerse in simmering water until jam is ready. Wash new, unused lids and rings in warm soapy water.

Transfer peaches and all accumulated liquid to a large pot. Stir in pectin and slowly bring mixture to a full rolling boil that does not stop bubbling when stirred. Cook for 1 minute, stirring constantly.

Remove from heat and stir in amaretto liqueur, adding more to taste.

Ladle peach jam into the prepared jars, filling to within 1/4 inch of the top. Run a clean knife or thin spatula around the insides of the jars to remove any air bubbles. Wipe rims with a moist paper towel to remove any spills. Top with lids and tightly screw on rings.

Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil and lower jars 2 inches apart into the boiling water using a holder. Pour in more boiling water to cover jars by at least 1 inch. Bring to a rolling boil, cover, and process for 10 minutes.

Remove the jars from the stockpot and place onto a cloth-covered or wood surface, several inches apart. Let rest for 24 hours without moving. Gently press the center of each lid with a finger to ensure the lid does not move up or down. Remove the rings for storage and store in a cool, dark area.