XC5 is not easy to follow. There is no straight way to explain it as it goes back and forth between php scripts and templates.
I still have hard time in some cases figuring out what's what and where does it come from.
Anyway look at this file - classes/XLite/Module/CDev/ProductAdvisor/View/NewArrivals.php - which shows the new arrivals products on site.
Code:
/**
* New arrivals block widget
*
* @ListChild (list="center.bottom", zone="customer", weight="500")
* @ListChild (list="sidebar.single", zone="customer", weight="160")
* @ListChild (list="sidebar.second", zone="customer", weight="110")
*/
ListChild tells the cart where to show the widget.
Take a look at - protected function isVisible() - it tells the cart where and when to show the widget. You can just overwrite this function in your module and remove the sidebar condition.
This is something to start with, you may need to do additional modifications though