Try working in mini sessions with smaller targets. Working in short bursts helps to maintain focus and motivation. 5-15 minutes may seem too little to some but for them its perfect.
This is a somewhat extreme example of a short session versus a longer one:
1. Complete concentration for a small amount of time.
2. Complete concentration for a small amount of the time then, trying to stop your mind from wandering for the rest of the session.
Things don’t always go this way but this shows an example of how things can be when you have a short attention span.
Studying this way can help keep things interesting and stop them from making the negative association of boredom with hifdh and Allah knows best.