2 Answers
As far as I'm aware, there's a site called Bookbite that operates on the "Advanced Copy Review" model. Here, you can review and get reviews for your book.
There's also pubby, but that's only for high-content books at the moment, whereas bookbite is high/low and audible.
However i've not used these services myself and i'm not sure how amazon views these sites
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Ask early readers, or your social media followers for honest reviews. You can also use ARC (Advance Review Copy) services to get reviews before launch.
Do not get involved with fake reviews or other promoted tactics.
You can also ask for a review inside your book. But anyplace you ask never ask for a 5 star or give some incentive.
Reviews have to be natural and organic.