What should the customer see before the product returns?
Leave the description and specifications on the page. Some people come back from a saved bookmark or from a link from a friend and still want to know what the product is, even if they will not buy it today. Next to the status add what you know about further sales, and if the supplier has given no date, say exactly that.
A temporarily unavailable product and a discontinued one are two different situations. Mark a discontinued one separately, and if you have a successor, link to it with an explanation of the differences, so that a customer coming back for the old model can check whether the new one suits them.
The status has to apply to the variant the customer chose. If boots in size 39 are on the shelf and size 38 ran out on Thursday, a person looking for 38 should see the stockout against 38, even if the product's overall status still shows green.
Check the ads that lead to the missing product too. A visit from an ad can still end in a purchase of a substitute or a sign-up for the notification, so compare the cost of the clicks with what those visits actually produced, and decide what the customer should do after landing on the page.
How to enable a back in stock notification
It depends on the platform. In WooCommerce, one of the options is the Back In Stock Notifications extension, described in the documentation on the WooCommerce site. In other stores, look for such a function in the settings or in the list of apps and modules.
Before you enable it, settle two things. The form should ask only for contact details and for which product, in which variant, the customer is waiting, and it should say plainly what the sign-up covers. If you send the messages by hand, someone has to watch the deliveries and remember the list.
Then run a test on one product. Set the stock to zero and sign up yourself. After you receive the goods, check that the email arrived, and only then show customers the promise of a notification.
A delivery date only if you know it
A customer will remember a date you give and come back to you with it if the goods do not arrive. If the supplier confirmed only a delivery plan to your warehouse, call it a plan and do not confuse it with a shipping date to the customer, because between the two there is still receiving the goods and packing the order.
The same rule applies to the bot. CartBot searches the connected catalog and skips products marked as unavailable, so instead of the missing boots it shows what can be bought. It can also collect contact details from a customer who prefers to wait. A collected address does not trigger an automatic message when the goods return, though, because that part has to be handled by the store or a separate tool. The bot works on data from the last synchronisation, so after a variant sells out, check when the change reached the chat and what happens when someone tries to add it to the cart.
The waiting list at your next order
Sign-ups say a lot about demand, provided you tidy them up a little, which means counting the interested people separately for each variant and removing repeats of the same person. Compare those numbers with sales before the stock ran out and with how long the stockout lasted, because a two-week gap will distort the comparison with a product that could be bought all month.
A waiting list is interest, and the orders come only after delivery and not from everyone. Some people will buy elsewhere or change their plans. When the goods return, count how many notifications ended in a purchase, and take that result of your own into account the next time you order ankle boots in size 38.
