cb111 wrote:What exactly is required for casting?
I've discovered clay / sand / tin & lead bars and have all the metalwork skills other than artifice but I dont see any casting moulds or anything.
Can you see Tinker's Shovel in Craft > Clothes & Equipment > Tools?
Instead of crafting the item you will be able to place a building in the ground (casting mould). To craft a Tinker's Shovel you will need soft metal, so you right click the mould with the soft metal bars (you need to have a lit stack furnace nearby).