[TYPO3-mvc] Fluid: Render custom template in current context to be able to use layouts

[roberto blanko]

Hello list,

I made my Fluid template configurable via Flexform. So in the end of the
corresponding action I'm simply doing this:

// If certain template was specified, use it
if ($this->settings['templateName']) {
     return $this->view->render($this->settings['templateName']);
}

The problem: Whenever I try to use layouts in the resulting template, I'm
getting the following error:

Tried to get a variable "sections" which is not stored in the context!

How can I set the context manually or what am I doing wrong here?

Thanks a bunch!