Wash and rinse glass jars (or plastic containers) and lids in the dishwasher or with hot soapy water. Dry thoroughly.
Cut the peaches in half from top to bottom. Remove the pit, then slice each half into ¼-inch slices. Dice the slices into ¼-inch pieces or smaller. (I like to use my chopper for this. See post above.)4 large or 5 medium-size ripe peaches
Measure exactly 3 cups of the diced peaches into a large microwave-safe bowl. Add the sugar and stir well for 1 minute. 4 ½ cups granulated white sugar
Place the bowl in the microwave on high power for 3 minutes. (Mixture will not cook, but will become hot enough for the sugar to dissolve). Remove from the microwave and stir well for another minute.
Allow this peach/sugar mixture to sit for 1 hour, giving it a good stir after about 30 minutes.
Take a taste to make sure the sugar is dissolved. If it still has a bit of a grainy texture, give it another 3-minute stint in the microwave, then stir until the sugar is well dissolved. (When the sugar is well-dissolved, the mixture will actually deepen in color and lose its "cloudiness". That's when you're ready for the next step.)
Mix the 1½ cups of water and pectin in a medium-size saucepan. Bring to boil on high heat, stirring constantly. Cook and stir 1 minute, adjusting the heat so the mixture doesn't boil over. Add the lemon juice and stir well. Then, add the pectin mixture to the peaches and stir for 3 minutes (no cheating!). 1½ cups water, 3 ½ ounces (98g) of powdered pectin (I use 2 boxes of SureJell which is readily available at most larger supermarkets. Each box is 1.75 ounces or 49g.) 1 ½ tablespoons fresh lemon juice
Fill all the jars to within ½-inch of the tops. Wipe off the top edges of the containers and cover with the lids. Let the jam stand at room temperature for 24 hours or until nicely set. Refrigerate up to 3 weeks or freeze up to 1 year. (If frozen, thaw in refrigerator before using.)