Pare skin from peaches. Remove pit and slice into ¼ inch slices.Place peach slices in a medium-sized bowl. Sprinkle lemon juice and vanilla over peaches. Stir sugar and salt together to combine. Sprinkle peaches with sugar salt mixture and toss gently.
Next, gently toss peaches with flour. Set peach mixture aside.
Roll out pastry round to 11-12 inch circle on lightly floured board. Pile peaches in center of pastry round.
Create a decorative spiral design, or other design with the peaches if you wish.Leave a two-inch border free around edge of pastry.
Fold the pastry up over the edges of the peaches to create a crust. Crimp edges as needed; (see pictures.)
Carefully move galette to a baking sheet.Brush surface of pastry with egg wash. Then sprinkle pastry with sanding sugar.Bake at 375 degrees for 34-40 minutes or until peaches are bubbling and crust is golden brown.
Let galette cool on wire rack for at least 10 minutes before slicing. Serve warm or cold.