Before we begin here's the live example. Write a review for "Darpan Agarbatti" by clicking here. Now just put this link on the website as a button and viola you have "Submit a review" button.

Now let's begin building this.

First of all, the business should be on Google, if it's not then make an account by visiting Google My Business

Then, get the unique place id of your business location by searching on map by clicking here.

Now place your unique id as shown in code below.

<!-- paste your unique place id at the end -->
<a href="https://search.google.com/local/writereview?placeid=">Submit Review</a>

<!-- example with Darpan Agarbatti -->
<a href="https://search.google.com/local/writereview?placeid=ChIJqXDLgYOJQTkRT1U49176R-w">Submit Review</a>

That's it, super simple. If you get stuck at any place, let me know on twitter.

See you later.