Google gives every verified business a short review link. In the Google Business Profile dashboard open "Ask for reviews" (or "Get more reviews") and copy the link; it looks like g.page/r/XXXX/review. That link opens the review dialog straight away, with the star picker on screen. Paste it above.
Asking works best at the moment of satisfaction: on the receipt, on a card handed over with the bill, on a sticker by the exit, on the back of the van for trades. A frame that says what you want ("Rate us on Google", "Happy? Tell Google") lifts response more than any design flourish.
Google’s review policies prohibit offering incentives for reviews and discouraging negative ones; a plain ask is fine. Do not put the Google logo in the code: use the colours or the stars instead.
Questions
Where do I find my Google review link?
Google Business Profile, then "Ask for reviews". The short link starts with g.page/r/ and ends in /review. Older place-id links also work but are much longer, which means a denser code.
Can I see how many people scanned the code?
Not with a static code. A lifetime editable code includes a scan counter and lets you swap the link if Google changes it.