Make the pate brisee: Put the flour, butter and salt in a food processor and process for about 5 seconds; the butter should still be in pieces. Add the ice water and process for about 5 seconds longer, just until the dough comes together; the butter should still be visible in the dough. Remove the dough from the processor and gather it into a ball. On a lightly floured surface, roll out the dough into a 16- by 18-inch oval 1/6 to 1/8 inch thick. Drape the dough over the rolling pin and transfer it to a large heavy baking sheet. Chill the dough until firm, about 20 minutes. Preheat the oven to 400 degrees. Make the filling: In a small bowl, combine 1/4 cup of the sugar with the ground almonds and flour. Spread this mixture evenly over the dough to within 2 inches of the edge. Arrange the plum wedges on top and dot with the bits of butter. Sprinkle all but 1 teaspoon of the remaining 1/3 cup sugar over the fruit. Fold the edges of the dough up over the plums to create a 2-inch border. (If the dough feels cold and firm, wait for a few minutes until it softens to prevent it from cracking.) Sprinkle the border with the reserved 1 teaspoon sugar. Bake the galette in the middle of the oven for about 1 hour, until the fruit is very soft and the crust is richly browned. If any juices have leaked onto the baking sheet, slide a knife under the galette to release it from the sheet. Spoon the preserves over the hot fruit and spread evenly with a pastry brush; brush some up onto the crust if desired. Let the galette cool to room temperature before serving.