If you don’t have enough flour for your recipe, just add 2 tablespoons of cornstarch to a measuring cup then fill it with what you have of all-purpose flour. If you’re looking for a gluten free option, you can substitute 1 cup of flour with 1 cup of almond flour and 1 extra egg. It’s important to note that the result will be a little more dense than usual. Oats are also a great substitute, and you can replace 1 cup of flour with ⅓ cup of quick or old-fashioned oats, but not instant oats. Finally, you might want to consider replacing 1 cup of flour with 1 cup of pureed black beans in brownie recipes. It sounds unusual but you won’t know until you try!