The Prophet ﷺ used to pray eleven rak'ahs at night, of which one was witr, then he would lie down on his right side.  

أَنَّ النَّبِيَّ ﷺ كَانَ يُصَلِّي مِنَ اللَّيْلِ إِحْدَى عَشْرَةَ رَكْعَةً وَيُوتِرُ مِنْهَا بِوَاحِدَةٍ ثُمَّ يَضْطَجِعُ عَلَى شِقِّهِ الأَيْمَنِ