out of stock and in stock

You can turn off manage stock at: Admin page > WooCommerce > Settings > Products tab > Inventory ? manage stock = unchecked.

If you have fixed prices but want to allow customers to let you know their options, you could look at product add-ons:
https://codecanyon.net/item/woocommerce-extra-product-options/7908619
One feature is a textarea where the customer can enter their requirements.

If however, your pricing is less predictable, you could use something like:
https://codecanyon.net/item/woocommerce-request-a-quote/6460218
The customer can build up a list of requirements and the plugin will send you an email with the list for you to work out a custom price.

In both cases, other similar plugins are available.

ok thanks lorro. will try it.