How is the prostration for forgetfulness performed if one adds to the prayer or subtracts from it?

The questioner : Peace be upon you.

The Shaykh : And upon you be peace.

The questioner : I would like to ask you, may you live long, about the prostration for forgetfulness when the prayer is excessive. How is the prostration for forgetfulness performed? Do I say the closing salam and then perform the prostration for forgetfulness, or is it after?

The Shaykh : For example, what is an example?

The questioner : The prostration is due when the prayer is excessive.

The Shaykh : May Allah do you good.

The questioner : I prayed five rak'ahs. Do I say the salam and then perform the prostration for forgetfulness, or do I perform the prostration for forgetfulness first?

The Shaykh : First, then perform the prostration for forgetfulness second.

The questioner : Good. And if the prayer is deficient, meaning you are uncertain, for example, you are uncertain in the prayer that you are praying four, and you are uncertain that you are praying three and the fourth is obligatory.

The Shaykh : And the evil is upon your suspicion, so raise it and lower it.

The questioner : I, may you live long, am praying a prayer like the four-rak'ah prayer.

The Shaykh : And what did you return to?

The questioner : I returned to it being deficient.

The Shaykh : Okay, if you prostrate after the salam.

The questioner : After the salam.

The Shaykh : Complete it and sit after the salam.

The questioner : May Allah reward you with good, O Shaykh, peace be upon you. I seek forgiveness from Allah.