I have the following .htaccess line, simple no indexes on root.
Options -Indexes
What do we add so it propagates to any sub directory instead of having to create one file for each? One .htaccess on root only.
The correct answer is
Options -Indexes
You must have been thinking of
AllowOverride All
https://httpd.apache.org/docs/2.2/howto/htaccess.html
.htaccess files (or "distributed configuration files") provide a way to make configuration changes on a per-directory basis. A file, containing one or more configuration directives, is placed in a particular document directory, and the directives apply to that directory, and all subdirectories thereof.