Sayyidi wa sanadi Shaykh Mohammad Taqi Usmani (may Allah preserve him) instructed a seeker who complained of missing the tahajjud salah,
‘Pray four units (rakah) of optional (nafl) prayers (salah) between the sunna and witr of esha with the intention of tahajjud. If you are able to wake up in the last part of the night pray tahajjud again.’
On another occasion he instructed,
‘Special effort should be made to wake up for tahajjud in the last part of the night. It will be completely fine to make up for the lost sleep after fajr prayers. However, until this habit is established make a routine of offering four units of nafl salah between the sunna and witr of esha.’
Saliks involved in completing their missed (qaza) prayers should also act accordingly. However, they should keep nafil to the minimum (2 rakah) and focus more on their qaza at this time also.