How do I make up for missed prayers whose number I do not know, and what are the recommended times for making them up?

If a prayer is missed due to a valid excuse, it must be made up, while observing the proper order. However, if it is missed intentionally without a valid excuse, scholars have differed regarding the obligation to make it up. The preponderant opinion is that it is not obligatory, but making it up is preferable and more cautious, to avoid disagreement. There is no specific time recommended for making up prayers, but hastening to do so takes precedence over supererogatory prayers and all other deeds, except for the five current obligatory prayers.