Self-rising flour is simply all-purpose flour with leavening agents added to help baked goods rise. As self-rising flour costs more than all-purpose flour, many people do not keep it on hand. In addition, the shelf life of self-rising flour is a year, so it's likely the bag will go bad before you've used it all. It's easy to make self-rising flour at home with just a few ingredients you likely already have in your cupboards.
Fill 1 cup with all-purpose flour. Drag the back of a butter knife across the top of the cup to level it. Use a measuring spoon and remove 2 tsp. of flour. Put the excess flour back into the flour bag.
Pour the scant cup of all-purpose flour into the bowl. Measure 1 1/2 tsp. baking powder and 1/2 tsp. salt into the bowl.
Using a mixing spoon, stir the baking powder and salt into the flour mixture. Stir until the ingredients are combined.
Place the self-rising flour into a plastic zip-close bag or storage container with a tightly sealing lid. Moisture and heat does ruin the flour, so it's important to keep it cool and dry until you use it.