The two most mentioned cloning apps are
SuperDuper! and
Carbon Copy Cloner ($27.95 and $39.99, respectively), but if you're only looking for a one-shot app, you can try
BackupList+ (Donationware), one of many less expensive options. (I use Carbon Copy Cloner, but I did a bit of beta testing for BackupList+ several years back and thought highly of it.)
(If you really want to go basic, I can re-post a Terminal command that V1 originally posted a bunch of years back.)
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Edit: Am I missing something, or is it odd that cloning apps are so expensive despite Time Machine? (CCC has actually actually gone from donationware to $40 shareware since TM was introduced.)