s.r. flour combines flour, salt, and leavening agent (baking powder,soda) into one step, so you don't have to pull out all that stuff and measure it when you are baking. it just saves a little time. here are a coupla recipes for making your own s.r. flour:

MAKE YOUR OWN SELF - RISING FLOUR
1 1/2 c. all-purpose flour
1 1/2 tsp. baking powder
1/2 tsp. salt
Combine all ingrdients. Mix well. Store in airtight container.

SELF-RISING FLOUR
10 lbs. plain flour
5 tsp. baking soda
1 c. baking powder
5 tbsp. salt
Mix together well. Use dairy buttermilk thinned 1/3 with water.