Where reviews belong in a Shopify store
On product pages, near the buy button rather than at the foot of the page. The reviews that reassure someone are the ones they see while they are deciding, not the ones they would have to scroll past the related products to find.
On the homepage, a carousel or grid under the hero. On cart and checkout-adjacent pages, a small floating badge does more good than a full section — it reassures without pulling attention away from the purchase, and it can be limited to exactly those pages.
Collect reviews from your customers too
The same widget has a Write a Review button. A customer rates you, types a few words and it appears in the widget, or you point them at Google and any other platform you have connected, or you offer both and let them pick. More on collecting reviews.
The natural place for this on Shopify is the order status page, where someone has just bought from you and is briefly well disposed towards you.
Star ratings in Google search results
Shopify is the case where review markup does exactly what people hope. The widget outputs Product schema with an AggregateRating, and Product is the type Google still shows star ratings for — the full explanation is here.
A product page with a star rating and a review count in the search result gets clicked more than the same page without one. That is the whole mechanism; there is nothing clever about it.