Hello,
To hide the out of stock products from your site follow the below steps:
1: Go to Woocommerce → Settings and click the Products tab
2: Click the Inventory link at the top
3: Check the Out Of Stock Visibility option to hide out of stock items
Screenshot: https://screenshot.net/7yykpij
If you have done all the above steps and the size filter still shown the sold out products then please refer the Woocommerce forum or try to find a plugin to solve the option.
Because this is the Woocommerce functionality and our theme does not influence. This is the way Woocommerce stock management works.
Best Regards.
.
