Objects without schema

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.5/ddl-schemas.html
Description:

In the last section of the document it says 'If you need to work with those
systems, then maximum portability would be achieved by not using schemas at
all.'.
But how do we achieve this? If I am not mistaken, all objects(like tables)
created in the database need to be created under one schema.

Thanks,
Joby