You can substitute plain flour if you cannot find self-raising flour.

如果你找不到自发面粉，可以用普通面粉来代替。

《柯林斯英汉双解大词典》

We have made it clear in our inquiry that the 1000 ton self-raising flour should arrive here by May 30, 2006, and that it should be packed in plastic bags of 5 kilo per sack for sales.

我们在信中已明确告诉贵方，我们拟购的1000吨自发粉必须在2006年5月30日前抵达这里，且必须用塑料袋包装，每袋5公斤，以便销售。

youdao

Self-raising flour contains a raising agent, but if you only have plain flour on hand, add 2 tsp of baking powder to 1 cup of plain flour.

自发粉里面已经含有发酵介质，如果你手头只有普通面粉，那么一杯普通面粉应加2茶匙泡达粉。

youdao