In a large pot, combine the diced peaches, sugar, jalapeños, lemon juice, and salt. Stir well and let the mixture sit for about 30 minutes to allow the peaches to release their juices.
After 30 minutes, add the fruit pectin to the pot and stir to combine. Bring the mixture to a boil over medium-high heat, stirring constantly.
Once boiling, continue to cook for 1-2 minutes until the mixture thickens slightly.
Remove the pot from heat and skim off any foam that may have formed on the surface.
Pour the jam into sterilized jars, leaving about 1/4 inch of headspace. Wipe the rims of the jars with a clean cloth to ensure a good seal.
Seal the jars with lids and process in a boiling water bath for 10 minutes to ensure they are properly sealed.
Remove the jars from the water bath and let them cool completely on a clean kitchen towel or cooling rack.