Butter or oil a 9×13-inch pan. Then line it with a single sheet of parchment across the width of the pan, allowing it to overhang the sides by a couple of inches. This will help you remove the bars from the dish when it has cooled.
Preheat oven to 325 degrees
Place the flour, sugar, and salt in a large bowl.
Using your hands, break up the Amaretti cookies into small pieces and work them into the flour mixture.
Pour the melted butter over the dry mixture and stir with a wooden spoon until the mixture is well combined.
Press the dough firmly and evenly into the bottom of the pan.
Bake for 15 to 20 minutes, or until the crust is lightly golden in color.
Remove the pan from the oven and immediately pour the custard into it while the crust is hot.