If you want to hide Our-Of-Stock item from BoostSales offers, please hide it by adding this tag to your product link:
How to add a tag to your product?
1. From your Shopify admin, click Products
2. Click the name of a product to edit
3. In the Organization section, select or enter tags for your product, using a comma to separate different tags. Any new tags will be created.
4. When you are finished, Save your product