Based on your comments- using Linux with a non-trivially small sized database, I will recommend you to use Percona XtraBackup ( https://www.percona.com/software/mysql-database/percona-xtrabackup ) to generate a copy of your current active database in a fast way and in an almost 100% hot way (no read or write blocking except to gather the binlog position, which normally should only take less than 2 seconds).
You can follow the steps at: https://www.percona.com/doc/percona-xtrabackup/LATEST/howtos/setting_up_replication.html (How to setup a slave for replication in 6 simple steps with Percona XtraBackup).
I asked those questions because the alternative is mysqldump/mydumper, but that will take more to recover for your data size (also XtraBackup didn't use to support non-linux). Here is how to do it ina hot way just in case: https://dev.mysql.com/doc/refman/5.5/en/replication-howto.html
A common mistake in both cases is thinking you need to stop writes or shutdown your master- you don't, just make sure you start replicating from the coordinates corresponding to the moment you took your backup (the end of XtraBackup run or the start of mysqldump/mydumper).
To prevent data drifts in the future consider performing regular consistency checks with tools such as pt-table-checksum or migrating to row based replication.
