Using log4net with SharePoint layout page applications is really no different from using it with other types of web applications with the exception that there really isn't a convenient way to initialize the logging configuration from your custom binaries.

The answer lies in the oft overlooked AssemblyInfo.cs file.

Add the following line to the file:

You may also want to add log4net binary to the /App_Bin directory of the WSS virtual directory (as well as the configuration into the web.config file of the application, of course).