How to create Steel Boning
Steel Boning is one of the many different craftable ingredients used in Tailoring that you need to make through Smithing. The Trivial for Steel Boning with the Smithing skill is 37, so you won't need to worry about raising your Smithing very far in order to make this.
One thing you will need to do though, is to complete the File subcombine before you're able to make the Steel Boning. It's a simple recipe that has an additional subcombine (but all vendor purchased items). You only need one File since it's never consumed nor broken while crafting.
Steel Boning (Trivial 37)
1 Small Brick of Ore
1 Water Flask
For anyone who doesn't feel like following the link for File above, here's the information on how to create it!
File (Trival 21)
Combine the following in any Forge to receive your File.
1 File Mold
1 Metal Bits