Scholars have gathered the incantations to be read after the prayers from the Hadith of the Prophet peace be upon him. For example, saying ‘استغفر الله’ three times, reciting the following once: أية الكرسي, سورة الفلق, سورة الناس
Tasbeeh-e-Faatimee etc
The best course of action will be to recite اللهم انت السلام ومنك السلام تباركت يا ذا لجلال والاكرام then perform Sunnah and finally complete the incantations. To delay Sunnah prayer after fard is disliked[1].
[1] Shami vol 1, pg 356