Ave - Mega Menu
The mega menu allows you to build any kind of layout thanks to the page builder. Simply go to Mega Menus > Add New and start adding elements/templates just like any other page.
If you'd like to use a fullwidth mega menu, just enable this option.
You can also add a nice hover effect on the mega menu. Navigate to Headers > Your Header and enable "Mega Menu Reaction" option.
If you've published the mega menu, you can assign it under Appearance > Menus.