Could you please elaborate on how to perform the prostration of forgetfulness (sujūd as-sahw)?

The prostration of forgetfulness (sujud al-sahw) consists of two prostrations, in each of which one says "Subhana Rabbiyal-A'la" (Glory be to my Lord, the Most High) three times. Scholars have differed regarding its timing: Imam Shafi'i held the view that it should be performed before the salutations (taslim) in all cases. Some scholars opined that it should be performed after the salutations, while others differentiated: before the salutations for deficiencies (naqs) and after the salutations for additions (ziyadah). As for Imam Ahmad, he gave the choice between prostrating before or after the salutations. For further details, one can refer to Sheikh Ibn Uthaymeen's treatise, "Risalah fi Ahkam Sujud al-Sahw" (Treatise on the Rulings of the Prostration of Forgetfulness).