The Prophet ﷺ made this very clear. Anas ibn Mālik (may Allah be pleased with him) reported that the Prophet ﷺ said:
"Whoever forgets a prayer should perform it as soon as he remembers it; there is no expiation for it except that."
He then recited the verse: *{and establish prayer to remember Me}* [Surat Tā-ha: 14]. [Sahih Bukhari 597, Sahih Muslim 684]
So the key points are:
1. Pray it immediately when you remember. Don't delay it further, don't wait for a "better time," and don't feel you need to do anything else to compensate. The makeup prayer itself is the expiation.
2. It remains obligatory. Missing a prayer out of forgetfulness or sleep is excused in terms of sin, but the prayer itself is still due — it must be performed. This is the position of the vast majority of scholars across the four schools.
3. Pray it as a normal Fajr — two rak'ahs, with the same recitation and format. You are simply performing it late.
4. If you wake up after sunrise, you still pray it right away. The Prophet ﷺ said regarding the one who catches even one rak'ah before sunrise: *"Whoever catches one rak'ah of the Fajr prayer before sunrise has caught the Fajr prayer."* [Sahih Bukhari & Muslim] This shows the prayer remains valid and due even at the edge of its time.
A practical note on the two Sunnah rak'ahs of Fajr: The Prophet ﷺ was extremely consistent with the two voluntary rak'ahs before Fajr — 'Ā'ishah (may Allah be pleased with her) said he was never more assiduous about any voluntary prayer than these two, and that they are "better than this world and all it contains." [Sahih Muslim 724] If you missed them along with the Fajr, many scholars hold that it is recommended to pray them after the obligatory Fajr if you still have time before sunrise, or after sunrise — but the obligatory Fajr itself is the priority.
Practical advice: Set a reliable alarm, and if you do oversleep, don't despair or delay — just get up, make wudu, and pray. You can use the prayer times section of your Al Muslim Plus app to confirm the Fajr window and set reminders so this happens less often. And if you'd like, you can keep a simple habit of reciting your nightly portion (hizb) of Quran — the Prophet ﷺ said that whoever sleeps through it and recites it between Fajr and Dhuhr, it is recorded as if recited at night. [Sahih Muslim]