New craigslist layouts are currently supported for custom themes only.

Once you have finished creating a flyer and publishing it using one of your designed theme, click Change Layout to get to the Craigslist Preview screen, then choose the layout that suits your style and click on Get HTML.

More information

You can choose the default layout for the craigslist html to be generated in. This setting will be applicable only if you choose a custom theme for you flyer. Click here to change the setting.