Be prepared and have contingency plans. So that you know what last minute changes you can make for the best results.
Have a list of products you know you can make (that you can source all the supplies in a timely manner) and keep them listed on your Etsy shop so you can keep selling them.
It’s kind of like a pre-sell. Make sure you know the delay in processing time and communicate that to your customers. Add a sentence saying that “this product will take an extra X days of processing before shipping. Thank you for your understanding”. Most customers will understand because Black Friday is a busy shopping season.
How quickly can you restock? Do you have a backup second supplier for similar materials?
Depending on how busy do you anticipate the period is going to be, you may want to contact some other suppliers so you have their contact in case you need some emergency inventory.
If you don’t anticipate that happening, then your effort would be better spent on creating higher demand and more traffic.
It’s inevitable that there will be some delays during busy shopping seasons due to high demand and large number of orders.
Good news is that most customers are aware of the situation and won’t mind waiting longer for their orders to arrive. It’s a good idea to put a paragraph in your ‘message to buyer’ to let them know what’s the estimate delay of their order.