How to create a barebones HttpApplication for ASP.Net (without Webforms or MVC)

Ok I am wanting to learn more about how ASP.Net works under the hood. I mean beneath MVC or Webforms and other such frameworks.

Basically I want to know how those frameworks are wired onto ASP.Net so that they work with IIS. What would be the bare minimum for creating a simple HttpApplication which worked with IIS and used neither MVC or Webforms? What is the bare minimum required to be in the Web.config? What would be added to Global.asax?

I actually meant to answer this question myself as I've done it. smartcaveman provides part of the solution.

What I did for web.config:

<?xml version="1.0"?>
<configuration>
    <system.web>
       <compilation debug="true">
       </compilation>
    </system.web>
    <system.codedom>
        <compilers>
            <compiler language="c#;cs;csharp" extension=".cs" warningLevel="4" type="Microsoft.CSharp.CSharpCodeProvider, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
                <providerOption name="CompilerVersion" value="v3.5"/>
                <providerOption name="WarnAsError" value="false"/>
            </compiler>
        </compilers>
    </system.codedom>
    <!--
    The system.webServer section is required for running ASP.NET AJAX under Internet
    Information Services 7.0. It is not necessary for previous version of IIS.
    -->
    <system.webServer>
    </system.webServer>
    <runtime>
    </runtime>
</configuration>

and then in global.asax:

protected virtual void Application_BeginRequest (Object sender, EventArgs e)
{
    if (Request.Url.AbsolutePath == "/test") 
    {
        var h=new Test1(); //make our Test1.ashx handler
        h.ProcessRequest(Context);
    }
    else
    {
        Response.ContentType = "text/plain";
        Response.Write("Hi world!");
    }
    CompleteRequest();
}

and then you can use ASP.Net handlers for content(as shown) or you can of course write your own replacement and write to Response yourself.

For reference, my working framework I made with a custom routing engine (and view engine) is in subversion here