There's no reliable black hat method that gives safe, genuine reviews. Fake or incentivized reviews can be detected and may get removed, or even put your profile at risk.
The best approach is to ask every satisfied customer right after completing a job. Send them your review link via WhatsApp, SMS, or email, and make the process as easy as possible.
If you're just starting out, even 5–10 authentic reviews with detailed comments can make a noticeable difference. Consistency matters much more than trying to get dozens of reviews overnight.