Here is a link to what is supposed to be an original Baker Rifle Sling. It is the only one on the Internet I’ve been able to find. However, knowledgeable people dispute this is from as early as the link states. The leather button on this sling is not called for in the 1802 Regulations for the Baker Rifle Sling which basically state the sling is supposed to be black, 1 ¾” wide and with a brass buckle.
The sling in this link MAY have been a later sling (Post Napoleonic War) or may even likely have been a late Brunswick Rifle Sling – according to some of the discussions.
http://www.ashokaarts.com/shop/rare-early-19th-century-baker-rifle-leather-sling-for-180015-patternAll the pictures of Reenactors in various units with their slings, do not include the leather button. Modern Reenactors are not all experts and some are far from accurate, but there seems to be almost no discussion/contention that the sling should have just one buckle and a sliding keeper, with the rear end tied around the rear sling swivel.
I am not sure if you are asking for detailed instructions on how to make the sling or not. There does not seem to be any on the Internet. However, if you go to the second photo set of the Enfield Rifle and Slings in this link, it shows the basic construction of British Rifle slings, though in different time periods. The first sling under the P1853 Enfield Rifle with sling shows the construction details of making an P1850 sling, BUT it looks unchanged from a Baker Rifle Sling except it is in white and of course the length of the sling would not fit a Baker. SPECIAL NOTE: The black sling with the button would not be correct for the Baker.
http://britishmilitariaforums.yuku.com/topic/14837/SniderEnfield-Sling#.UweyRumPJhhI have no connection with the next two linked companies, whatsoever.
Here is a link to a supplier of British Military Leather goods in your country. The Baker Rifle sling mentioned does not seem to be illustrated, but I’m sure you could contact him with questions, if you wish to purchase the sling.
http://www.nzrifle.com/vma_leatherware.htm Here is a link to another reproduction Baker Sling, though the photo quality is not good enough to see much of the construction details of the sling.
http://www.re-enactmentsupplies.co.uk/index.php?route=product/product&product_id=270 Making a good reproduction Baker Rifle Sling would not be extremely difficult for someone who has some leather working experience, including amateurs. I would think finding or making an accurate copy of the buckle might be the hardest part.
I am not sure, but are you also asking for how to mount the sling on the rifle? If so, please reply and I can describe it for you.
Gus