For the floor, I salvaged heavy duty plastic pallets from my day job at Cielo, a bottled water company. They get tons of them, and they are stacked up in the warehouse. Very cuttable, and very solid. Then a layer of wire netting with gravel on the top. The hole on the left is for the foundation of the anvil, which needs to rest on the ground. (So, no, I can’t just hook up the trailer and drive away, any more!)
The back door was a problem. I intended it to raise up, to provide light and more shaded/protected workspace at the back of the forge. But it was just too darn heavy! So I created a winching system, and forged a simple rod to distribute the weight evenly.
The last large tool to be put in place was the flypress. Because it was the heaviest! I used a storage box off an old Cielo box, turned vertical and framed with heavy wood, to create a stable base. You can also see the vise on the left side.