Measure out 3 cups of all-purpose flour.

From the measured all-purpose flour, remove 6 tablespoons this can go back into the flour bag, we will not be using it

Put the flour (minus the 6 tablespoons) into a sifter set over a bowl.

Replace the six tablespoons of flour that you removed with six tablespoons of cornstarch in the sifter.

Sift the flour and cornstarch together. I like to sift onto a large sheet of wax paper, This makes it easier to transfer the flour-cornstarch mixture back into the sifter.

Repeat the sifting process, ideally, the mixture should be sifted 5 times, this will guarantee your cake flour is well incorporated and aerated.