im a newbie here and have no idea what allowed and not allowed
Then you should ask first.
There are 43,528 knives for sale on eBay today. If we allowed all those sellers to post links to their auctions, our poor discussion forum would simply collapse.
There are three good ways that a custom maker can advertise here on bf.c.
1) Post pictures of your work in the appropriate forums. But, keep in mind that those posts must not be advertising. You can not list a price. You can not offer the knife. You can not offer you services overtly. You can simply post a picture saying, "Look what I did." This will encourage potential customers to contact you by e-mail outside of the forum and you can work out your deals that way.
2) Build a nice website for yourself (this is neither hard nor expensive) and put a modest link to that site in your signature line. Then, partipate intelligently here at bf.c. Every post you make will have your website in it and many people, impressed by your intelligent, knowledgable, thoughtful, and helpful posts, will click on your link and see your site.
3) Buy a dealer membership here at bf.c. Now you can advertise within specific limits which will be explained to you at that time.