This document only exists to write the SQL sentences explainded by burleson here: http://www.dba-oracle.com/t_rman_149_flasbback_query.htm
But formatted and not as he uses to write with numbers or in-completion that will make the query unusable … (fu***ng stupid).
So here we go:

SELECT * FROM SCHEMA.TABLE
AS OF TIMESTAMP to_timestamp('23-03-2020 11:00:00','dd-mm-yyyy hh24:mi:ss')
WHERE SOME_FIELD LIKE 'SOME FILTER'
/

What you have to know is that the as of timestamp must follow the from and before where sentence.
cheers!