==== Leavening Agent ====

as a substitute for 'self raising flour' use flour and a leavening agent...

  * Baking powder: For every 375 grams of flour, add 10 grams of baking powder
  * Baking soda & cream of tartar: Mix 1 gram of baking soda and 1.5 grams of cream of tartar in place of 5 grams (1 tsp) of baking powder
  * Baking soda & buttermilk: Mix 1 gram of baking soda and 125 grams of buttermilk (or yoghurt) in place of 5 grams (1 tsp) of baking powder 
  * Baking soda & vinegar: Mix 1 gram of baking soda with 2.5 grams of vinegar or lemon juice in place of 5 grams (1 tsp) of baking powder
  * Baking soda & molasses: Mix 1 gram of baking soda with 110 grams of molasses or honey in place of 5 grams (1 tsp) of baking powder 

====specifically substituting spelt====

To substitute white spelt flour for self-raising wheat flour, convert your wheat recipe by either reducing liquid ingredients in your
recipe by 10–15% or increasing flour quantity by 10–15% then sift in ¾ teaspoon of baking powder with each cup of white spelt flour.

see also https://www.wikihow.com/Substitute-Spelt-Flour-for-All%E2%80%90Purpose-Flour