.....what?
Seriously though. What?
To make a Shield - which can be done in Standard gameplay, and customers can even ask to buy it (albeit, There's still an issue with them properly clearing out of the shop after waiting and accepting both items (since they will also ask for a weapon and there's a part in their script that has them "wait" after receiving the item - that likely interferes with them properly leaving after they get both)
Anyway.
You take a Full Wood Log (not Firewood)
place it onto the wood working station - turn it into the shield type you desire (or a crate)
you can set that aside or place it in the shop
you need FIVE ingots, heated, or any one type (From what I've heard, I haven't tried combining different metal types because of that)
You need TWO of these ingots heated and on the anvil, to make the specific Shield Rim/frame - Which can either be cooled and set aside, or you can go ahead and set it in the shop too, attaching it if you want (on workbench)
You then need THREE Ingots heated for the other three parts, however they need to be done SEPARATELY - Once for Boss, Once for Wrist Enarmes(grip?) and lastly, once for hand enarmes (other grip?) - Which then must all be cooled, and attached.
If done properly, You should be notified in the corner like with any weapon - that you've successfully created said shield.
And like with any item in which the "created" notification appeared for, You can sell it, of course, Shield is hardest to pawn/sell off, since its still rarely asked for.