The Prophet ﷺ used to pray eleven rak'ahs at night, ending them with one rak'ah of witr, then he would lie down on his right side.
أَنَّ النَّبِيَّ ﷺ كَانَ يُصَلِّي مِنَ اللَّيْلِ إِحْدَى عَشْرَةَ رَكْعَةً يُوتِرُ مِنْهَا بِوَاحِدَةٍ ثُمَّ يَضْطَجِعُ عَلَى شِقِّهِ الأَيْمَنِ