Teasers are blocks of generic global sections (built with Elementor) that can be published somewhere in the product catalog listing.
First, make sure to create the generic global sections in Rey theme > Global sections.
Head over to Customizer > WooCommerce > Product catalog – Content and create new teasers eg: https://d.pr/i/urPZGN .
You can pick the size, row number and position in the row. You can also assign it on product categories and choose if you want to show in the Shop page or not.
These teasers will be shown before or after the product item in the listing. Such as the global ones, you can choose to have different sizes.
In case you are unable to determine where this content is added from, you can browse the products in the backend and you will notice a hint right under the product title eg: https://d.pr/i/UVN9tw .
To add one, edit a product in the backend and click on the Catalog Display tab eg: https://d.pr/i/TD8eut .