Go to your current theme folder and create new layout file for main page.

Go to Developer -> Zones and create new zone:

• name - name of menu. Choose anything you like
• key - name of zone for use in PHP code. Typically the same name without special characters and with underscores instead of spaces
• layout - choose your newly created layout
• associated module group - use standard
• associated module - use content_management

Move your new zone to the top (it should be the first zone).

If your main page contains no manageable text (eg. only flash), you may left blank associated group and associated module fields. This will tell the system that zone have only one page and all required content is hard coded into template layout. In such case you need to skip step 3.

Go to Standard -> Menu management and add one page to that zone.

That's it. Your website will start with new (different) layout.