[kovidgoyal]

The simplest way to manually create a TOC is just add a section like

<ul>
<li><a href="#chapter1">Chapter One</a></li>
<li><a href="#chapter2">Chapter Two</a></li>
.
.
.
</ul>

Near the top of the HTML file where you want the TOC to appear. You also have to identify the actual chapter titles in the text like this

<h2 id="chapter1">Chapter One</h2>

You can of course use any text not necessarily Chapter One

Note that you can manually force a page break before any HTML element by adding style="page-break-before: always" to the HTML tag

<p style="page-break-before: always">Some paragraph...</p>

So to consolidate, your HTML file should look like this:

<h1>Book Title</h1>
...
<h2>Table of Contents</h2>

<ul>
<li><a href="#chapter1">Chapter One</a></li>
<li><a href="#chapter2">Chapter Two</a></li>
.
.
.
</ul>

<h2 style="page-break-before: always" id="chapter1">Chapter One</h2>
.
.
.

<h2 style="page-break-before: always" id="chapter2">Chapter Two</h2>
.
.
.

There is an example here http://calibre.kovidgoyal.net/downloads/html-demo.zip