The method is one set of 2 prostrations.
Even if several forgetful Wajib errors occurred in the same prayer, one Sujud al-Sahw set is sufficient.
After the 2 prostrations:
• sit again;
• recite Tashahhud;
• according to the chosen view, complete Salawat and dua;
• then give the final Salaam.
Do not multiply the number of Sahw prostrations according to the number of mistakes.