The "five fortresses" approach to Quran memorization is a structured technique that involves planning which pages to memorize, following a specific memorization process, and implementing a systematic review schedule.
This method incorporates reading directly from the Mushaf, listening to proficient reciters, practicing repetition, and then reviewing memorized portions without referring to the text.
There appears to be nothing objectionable about this approach. On the contrary, it is a beneficial method that keeps a Muslim connected to the Quran daily and helps establish consistent recitation habits.
Methods and tools for acquiring knowledge and memorizing the Quran are permissible by default, as long as nothing in Islamic law prohibits them.
Shaykh Ibn 'Uthaymin (may Allah have mercy on him) explained this principle clearly:
"When a method is not prohibited and proves effective, there is no issue with using it. Methods differ from objectives — Islam does not need to explicitly approve every possible technique, since the ways of achieving good are limitless. Any method that leads to good is itself good."
Liqa' al-Baab (15/30)
It is important to recognize that different individuals may benefit from different techniques. What works well for one person may not suit another. Each individual should identify the approach that best matches their learning style. As the Prophet (peace be upon him) said: "Pursue what benefits you, rely on Allah, and do not give in to helplessness."