The first thing to remember what the Board's role is.
The role of a board is to agree an annual operating plan (budget) and strategy and to periodically (usually quarterly) review progress and make adjustments when necessary. The board’s job is also to confirm the financial results (audit), to manage the compensation of key executives including the CEO. Finally, the boards job is to vote on key considerations including budgets, financings, legal issues and on rare occasion — hiring & firing the CEO.
Usually an early stage Board consists of three members and founders' want to retain control of the Board. As such the Board composition usually consist one founder (usually the CEO), an investor and an independent chosen by the company and investor. The independent board member should have a background that allows them to provide relevant guidance and feedback.
If your startup doesn't have an outside investor, I would recommend having an advisory board instead. They can focus on providing feedback and advise instead of oversight. In this case I would make sure the advisory board consist of the founder and several people who have experience and credibility in areas that the company needs help with.