File upload referencing record that is not inserted yet

i have a question that i couldn't find a satisfying answer.

i have a "Add Product" screen, this product has zero or many images. In this same screen there is the upload option.

My question is: how can i upload pictures to the product, if i don't have it`s id yet? since it is not saved on database yet.

Is there any best practice for this situation?

Thanks in advance