Preheat oven to 400 degrees. Line a rimmed baking sheet with parchment paper. Make the crust:  in a food processor, combine flour, salt, and sugar; pulse a few times to combine. Sprinkle butter pieces on top of flour and pulse several times until the mixture is coarse and sandy. Drizzle in water, processing on low speed until the dough begins to come together in a ball. If it seems too dry, add another tablespoon of water. Wrap dough tightly in plastic wrap and chill a minimum of 20 minutes (up to1 hour), then remove from fridge and roll the pastry out into a rough circle about 1/8-inch thick. Carefully transfer to the parchment-lined baking sheet. For the filling, whisk together the almond flour, all-purpose flour, and 1/4 cup sugar.  Spread evenly on top of the crust, leaving a 2-3 inch border. Arrange the plum slices on top of the almond mixture. Sprinkle first the lemon zest and juices over the filling, then the remaining 3 TB sugar. Fold the edges of the crust back over the top, pinching the dough back together if it cracks. Bake at 400 degrees for 45-60 minutes, until the crust is golden brown. It’s okay if the filling has leaked out of the sides – that just lends to the rustic feel of the dessert. While the galette is still hot, brush the fig jam on top of the filling and crust. While the galette is cooking (or cooling), crisp the prosciutto. Mist a small pan with olive oil and set over medium heat. Add the diced prosciutto and cook, stirring frequently, until brown and crispy. Drain on paper towels. Sprinkle the crispy bits on top of the galette just before serving. Serve slightly warm or at room temperature.