In a mixing bowl, stir together the flour and salt.  Using a pastry blender, cut in the shortening until you create pea-sized pieces.

Moisten a little bit at a time by sprinkling a section with 1 tablespoon of water; gently toss with a fork.  Push the moistened dough to the side of the bowl.  Repeat moistening dough, using 1 tablespoon of water at a time, until all of the dough is moistened.  Form the dough into a ball.

 Preheat oven to 375°F.

On a large piece of lightly floured parchment paper, roll pastry into a 13-inch circle.  Slide the paper with the pastry onto a baking sheet.  Set aside.

For the filling, add the peaches and lemon juice to a large bowl.  Toss until coated.  Mix the sugar, flour, and nutmeg in a small bowl.  Sprinkle the sugar mixture, along with the chopped thyme, on top of the peaches.  Toss again until all of the peaches are coated.

Mound the fruit filling in the center of the prepared pastry, leaving the outer 2-inches uncovered.  Fold the uncovered pastry up over the filling, pleating the dough as necessary.  Use the paper to lift the dough, if need be.

Sprinkle the filling with the sliced almonds.  Lightly brush the pastry top and sides with milk and sprinkle with additional sugar.

Bake for 50 to 55 minutes or until filling is bubbly and crust is golden.  If necessary, cover the edge of the tart with foil for the last 5 to 10 minutes of baking to prevent overbrowning.

Cool for 30 minutes on the baking sheet on a wire rack.