Preheat oven to 350 degrees Fahrenheit.

To make the crust, combine flour, salt, sugar, and butter in a food processor until it forms a dough. Spread evenly in a baking dish and bake for 18 minutes, until just golden.

While crust is baking, prepare the filling. Melt butter, then add sugars and salt and mix to combine. Let stand for 10 minutes, then add oats, chocolate, eggs, coconut, and vanilla. Spread evenly over the half-baked crust, then bake for an additional 15 to 20 minutes until firm. Let cool completely before cutting. Cut into squares, then dust with powdered sugar.