Comments are not active in Lay Theme and therefore i dont believe reviews are active within Woocommerce. They may come in the future as Woocommerce integration improves.
Please be aware that any updates will refresh the Changes done to your functions.php file. Because of this i would suggest using > Lay Options > Custom CSS & HTML > to apply reviews to your site. I understand the need to try different things out though.
If you would be willing to insert the reviews manually, this can be easily done via +More > HTML:
Screen Shot 2020-09-14 at 2.50.29 PM.png
The Gridder isn't applied to single product pages yet. For reviews on these pages i would suggest jQuery
https://laytheme.com/documentation.html#custom-javascript
(Note: I understand these would be Customer Inputted reviews)
Sorry for the inconvenience while Woocommerce Integration advances, best wishes 🌝 Richard