Well, instructions for Recollective Awareness Meditation can easily be found online

. For example: https://santamonicaacupunctureandmeditation.com/meditation/instructions/#:~:text=Close%20your%20eyes%20and%20bring,to%20go%20where%20it%20will.
So, basically, you let your attention go wherever it wants. Then, after the session, you write down notes about what you experienced during the meditation.
So, the instructions are minimal (in order to prevent the tension that appears when instructions and your actual sensate experience come in conflict). However, the journaling is retroactively strenghtening the mindfulness: by making yourself remember what you experienced, the next time your mind will be drawn to experience it with more detail, notice patterns etc. This approach is implicitly aimed at raising the mindfulness of thoughts and emotions.
I really like when Siff says he doesn't claim this is some kind of "best" meditation, and that he expects that practitioners will evetually "go on". But the value of the technique is to relax the tensions in meditatior's approach to practice (fixations on "right instructions", "shoulds", rigid beliefs, judging etc.)
What made the strongest impression on me, however, is the originality of conceptual framework presented in his book (e.g. the detailed explanation about "impasses" in meditaton).