In a large bowl, gently toss together the sliced peaches and strawberries, sugar, sliced almonds, cornstarch, and almond extract until fruit is fully coated in mixture.
Lightly flour a sheet of parchment sized to fit a standard baking sheet.
Flour surface of dough lightly and roll out on parchment to a 12? round, adding more flour as needed to prevent sticking. Dust surface with 2 tablespoons gluten-free flour and arrange fruit slices concentrically on top of dough, overlapping pieces slightly and leaving a 2” border around the outside edge. Pour any remaining filling/juices over the fruit once done.
Fold and pleat dough around edges of galette, overlapping outer border of filling.
Transfer galette to refrigerator to chill for 10 minutes. Meanwhile, preheat oven to 400ºF.