Step 1: Prepare your canning equipment by sterilizing 4-5 half-pint (8oz) jars, lids, and rings. Keep them hot until ready to fill.
Step 2: Blanch the peaches to remove skins: Bring a large pot of water to a rolling boil. Carefully drop peaches into the boiling water for 30-60 seconds. Immediately transfer them to an ice bath. The skins should slip off easily. Peel, pit, and slice the peaches into desired chunks (aim for about 6 cups of sliced peaches).
Step 3: In a large, heavy-bottomed pot, combine the sliced peaches, granulated sugar, and fresh lemon juice. Stir gently to combine. Let the mixture sit for 30 minutes to 1 hour to allow the sugar to draw out the peach juices.
Step 4: Place the pot over medium-high heat. Bring the mixture to a full rolling boil, stirring constantly to dissolve the sugar. Reduce heat to medium and continue to cook, stirring frequently to prevent sticking, until the preserves thicken. This can take 30-60 minutes or longer. To test for set, place a small spoonful on a chilled plate and push it with your finger; if it wrinkles, it’s ready. The temperature should reach approximately 220°F (104°C).
Step 5: Carefully ladle the hot peach preserves into the hot, sterilized jars, leaving 1/4 inch of headspace. Wipe jar rims clean with a damp cloth. Place new lids and rings on the jars, tightening finger-tight.
Step 6: Process the filled jars in a boiling water bath canner for 10 minutes (adjust time for altitude if necessary). After processing, turn off the heat, remove the canner lid, and let the jars sit in the hot water for 5 minutes. Carefully remove jars to a wire rack to cool completely for 12-24 hours. Do not disturb them during this time.
Step 7: Check seals: Lids should be concave and not flex when pressed. Any unsealed jars should be refrigerated and consumed within a few weeks. Store sealed jars in a cool, dark place for up to 1 year.