There are several common reasons for a slow build:
Unnecessarily Files: Look for large file warnings during the scan report step. Go through the list and determine if you need to backup that file. Go back to the package creation screen and add the full path of any large unnecessary files to the ignored file list. Backups created by other backup plugins should not be backed up. Also look for larger log files and data that is not needed for a proper restore.
System Zip: The zip routine built into the operating system is much faster in most cases then trying to use PHP. Go to the Settings/General page. Ensure “Archive Engine” is set to “Shell Exec” instead of “ZipArchive”.
Slow Server: If you’ve tried the options above but your builds are still slow, chances are if you’re on a budget host then the server is currently overloaded. Please contact your host’s support and ask to move servers or have the slowdown investigated. If you have access to your on server or VPS consider increasing the PHP memory_limit.
What can I do for issues with migrating a large site?
Recommended hosting providers for Duplicator?