The Place of the Prostration for Forgetfulness Before and After the Closing Salam

Question:
Which is preferable: should the two prostrations for forgetfulness be performed before the salam or after the salam?

Answer:
It varies. If he said the salam due to a deficiency, it is performed after the salam.
You mean some people perform them before the salam?
The Shaykh: It is permissible to perform them before the salam and after the salam.
And which is preferable?
The Shaykh: But if there is a deficiency, it is performed after the salam. If he said the salam after three rak'ahs, then was reminded and completed the prayer, his prostration is after the salam, or similar to that. That is, if he forgot and said the salam in that state, his prostration is after the salam.
As for a forgetfulness within the prayer, it is better to perform it before the salam. For example, if he left out the first tashahhud, or if he was in doubt whether it was three or four rak'ahs and they reminded him and he completed it, it is better to perform it before the salam.