To prepare the meringues: Preheat the oven to 250°F. Line two baking sheets with parchment paper.
In a spotless electric mixer bowl, beat the egg whites with the salt until frothy, about 2 minutes. With the beaters running, add the sugar 2 tablespoons at a time, scraping down the sides of the bowl every so often. Continue beating until very stiff peaks form and it looks satiny, 8 to 10 minutes.
Fill a pastry bag fitted with a star tip with the meringue, and pipe twelve 3-inch circles onto the prepared baking sheets, about 2 inches apart. Then pipe another ring on the outer edges of the circles to form an edible dish that will hold the berries and cream. You may also drop 2 or 3 spoonfuls of meringue onto the prepared baking sheet about 2 inches apart, and then with the back of a wet tablespoon, make an indent in the center to form a dish.
Place the meringues on the center rack of the oven and bake until they are set and pale almond in color, about 1½ hours. Turn off the oven. Leave the meringues in the oven 30 minutes longer. Remove from the oven and let cool completely on a rack. With a thin pancake turner, carefully slip the meringues off the paper and store them in an airtight container until ready to serve.
To prepare the filling: In a cold mixing bowl, beat the heavy cream, confectioners' sugar, and vanilla until thick, about 4 minutes. Cover and refrigerate until assembly.
Set aside 12 perfect strawberries for the garnish. Slice the remaining strawberries into a large bowl, sprinkle the sugar over, gently stir, and let stand for 10 to 20 minutes. Taste and adjust the sweetness. Set aside until ready to assemble.
Fold the berries into the whipped cream and fill the meringues. Garnish each with a perfect strawberry and serve at once.