Preheat the oven to 350 degrees F. Spray a 9-by-13-inch pan with nonstick cooking spray.
In a mixing bowl, combine the almonds, graham cracker crumbs and butter with fork until fully incorporated. Press into the bottom of the pan.
Using a handheld or a stand mixer, beat the cream cheese until smooth and no lumps remain. While mixing, add the eggs, sweetened condensed milk, lemon juice, almond extract and flour. Mix until fully combined. Reserve a heaping tablespoon of batter and pour the rest over the graham cracker crust.
In a mini food processor or blender, puree the peaches along with the reserved tablespoon of batter until completely smooth. Using a tablespoon, drop spoonfuls of the peach mixture over the top of the cream cheese mixture. Using the tip of a butter knife, gently swirl the peaches through the filling to create a marbled look.
Bake until the center is set, about 30 minutes. Cool to room temperature before transferring to the refrigerator to chill throughout. Cut into bars and serve chilled.