aa-globe

This plugin has no settings. 
Just activate the plugin and check if sold out items have moved to the bottom of the list.

Catalog Sorting by Stock Status – In Stock First, Sold Out Last

This plugin changes the sorting of a catalog (or product category) so that out-of-stock items are always at the end of the list

theseforumslookquitehelpful

This plugin was built to add a “Random” Product Sorting Order to WooCommerce with working pagination.
Other solutions I found that added a “Random” Product Sorting Order did not preserve pagination.
This plugin will sort your WooCommerce Products in random order. A random sort has a transient life of one hour. (In version 0.9.1, the duration is not a settable option. It is fixed at one hour.) Every hour a new random sort is generated. Pagination works as expected, meaning each WooCommerce Product will be diplayed once and no more than once.
This plugin requires the WooCommerce plugin.

WooCommerce Random Product Sorting with Pagination

Add a "Random" Product Sorting Order to WooCommerce with working pagination.

Catalog Sorting by Stock Status – In Stock First, Sold Out Last vs WooCommerce Random Product Sorting with Pagination