Displaying Sub Categories Full Width

I have my store arranged where products are only visible in the last possible sub category (in other words there are never products and sub-categories visible at the same time). At this level, the filters are visible on the left side bar, which is fine.

However, when I ONLY have sub categories displayed, they are shown on the right 3/4 of the screen while there is a ridiculous looking column of “nothing” on the left side.

I want these sub categories to occupy the full width of the screen. Is this possible?