I am not in charge in any way but I have an opinion.
I've read other people say that Lemmy is a link aggregate and not an OC social media site(I don't necessarily believe that, I believe if that were the case then we wouldn't have "communities" at all). If that is true then I don't see why you can't post anything related to leathercraft here.
Let's be honest, there are very few posts here to begin with. Probably because there isn't a lot of exposure to leathercraft on Lemmy. People need to be exposed to a hobby in order to be interested in it.
I feel as long as the quality of the leathercraft and the post is up to par then feel free to post it. Perhaps with enough nonOC content we will get more OC content.
If it's a post to a store I feel differently about that. I'll probably downvote that. I'd say post a photo or series of photos and if anyone is interested you can have a discussion of the product. Which may then include the link to the store. Or maybe only link to stores privately, again I'm not in charge.
Edit: Perhaps the post title may be similar to classic art posts.
"Name of art(Product)" - "Artist(Person/Maker/Business)" -Year?(probably doesnt matter unless it's historical)
Something like that for other peoples work.