The Bill of Lading (BOL), is essentially a document that has the specifics of the shipment on it.
Amazon should generate the BOL for you on the morning of the pickup date. The BOL is also only during LTL shipments.
If you listed your supplier as the contact person for shipping the product, then the BOL will automatically be emailed to them once it is generated.
Here is a link which goes over it in more detail: https://sellercentral.amazon.sg/gp/help/external/201022330?language=en_SG&ref=efph_201022330_cont_201074410
Do SPD shipments have a BOL?