You must have "Full Access" or "Limited Access - Website" permissions to delete Layout Containers.
NOTE: Deleting a layout container will permanently delete any page elements inside of it too.
Sign in to your site and go to the page that has the Layout Container on it that you would like to delete.
On the left-hand side, turn on Edit Mode.
In the right-hand corner of the Layout Container, click on the gear icon.
Type 'DELETE' to confirm, then click Delete.