Either in addition to, or within specifications or introduction, a listing of assumptions and design parameters (basically restating the problem you've been given and the interpretion you've given to the problem) would be helpful.
Also, it isn't uncommon to have an appendix or two providing background or detailed calculations of a side point, and a bibliography, if any substantial proportion of your project buildings on published prior works in the field.
An example of a very big (group) design project for student engineers in a final capstone project at the U.S. Naval War College is found here: http://web.nps.navy.mil/~me/tsse/files/2001.htm and may give you some presentation ideas (although an individual project would ordinarily be less polished). It had:
Cover Page
Abstract
Table of Contents
Executive Summary
Requirements
- Mission Needs Statement
- Operational Requirements Document
Analysis of Alternatives
- Alternatives Under Review
- Payload
-- Definition
-- Assumptions
- Resulting Hull Sizes
- Measures of Effectiveness
- Recommendations and Alternative Selection
- Faculty Decision for Design
Concept Design
- Broken down into eight subsystems and subsubsystems within them plus a section on the integration of the subsystems into the whole.
Analysis and Trade Studies
- Detailed re-examination of the elements identified in the concept with potential vendors.
Conclusions
References
Appendixes A-D (Typical results of analytical tools used, detailed calculations for two subsystems and an extended discussion of assumptions used to generate the payload requirements in the mission statement)
Initial Distribution List