One issue with the flexibility of PRINCE2 allowing managers to leave things out. However, what you do in simple projects is the same as any other project, and that is to adjust the degree to which the processes and activities are carried out. This is scaling and applying appropriate, intelligent and professional planning and control.
✔ Verbal communication as opposed to written reports, information may be dispensed vocally often in a simple project.
✔ Reduce the size and complexity of reports by combining different sections, where appropriate.
✔ Intelligent selection of planning techniques to use as a project may not need all of them.
✔ There may be a significantly smaller number of delivery stages, maybe only one.