Custom asterisk.conf location

I understand that custom modules and config directories must be kept in asterisk.conf.
How one may point a proper asterisk.conf file with custom settings of those directories?

The default one is in /etc/asterisk/ directory, but what if user cannot use this directory.

Start the Asterisk process with the -C flag and specify the location.

For more options:

/usr/sbin/asterisk -h