Content Bottom widget with horizontal layout?

In Twenty Sixteen theme the default content layout for the Content Bottom 1 & 2 widgets is vertical. I’d like to change this to a horizontal layout, but I don’t see where content is being forced to vertical in either the .php or .css.

Under ‘.content-bottom-widgets .widget-area’ I set ‘width: 100%;’ but this doesn’t affect the content layout.

Thanks in advance,
Tim