DIY Baking Steel?

Steels are alloys of different compositions of iron carbon and other metals. Not all steels are considered safe for food as some contain metals or additives that could in some circumstances leach into food, so not just any steel will do.

Baking steels are usually made of A36 steel or stainless steel:

• A36 is not stainless, it's commonly used for structural members but is also a popular choice for restaurant griddles. It isn't stainless so it will rust, so you will first have to get the rust off and then oil the steel after every use or season it. It's cheap and has good conductivity
• Stainless steel (316 or 430, not 304 as that tends to pit) is more expensive and doesn't conduct heat as well as A36 steel, but it's a lot less maintenance as you don't have to worry about keeping up the seasoning. You can wash these to clean them

Depending on where you are you can get just about any steel cut and shipped to you at any size and thickness. If you ask the shop may soften the edges for you, which is important for safety, if they don't you can do it yourself with an angle grinder and a metal grinding disc. This sounds scary but it's actually pretty easy, just wear eye protection, gloves and old clothes. Whatever steel you buy will need to be cleaned to get any coatings or industrial by-products off before use.