Add peaches to a bowl and sprinkle with sugar and lemon juice. Stir well to combine, then allow to rest for 30 minutes to an hour, stirring once or twice.
Drain peach juice into a measuring cup to get 1 cup of juice (you can drink any additional juice, or save it for another recipe like my steak marinade).
Pour juice into a saucepan and stir in cornstarch. Cook on medium heat for a few minutes, until thickened.
Remove from heat and stir in the butter, salt and almond extract.
Pour peaches into a baked 9'' pie shell and pour the thickened sauce on top. Place a piece of plastic wrap directly on top and chill for at least one hour before serving.
Serve with whipped cream on top, if desired.
To make ahead: Prep the entire pie up to 1 day ahead of time and store in the refrigerator.To freeze: Once pie has cooled completely, cover it tightly with an extra layer of plastic wrap and tinfoil. Freeze for 2-3 months. Allow to thaw completely before serving.