Compressed Earth Blocks
In the real world, there is a machine made of metal that can take a recipe of different components - such as soil and wood ash to make fly bricks, or soil and cement, and sand for clay bricks with enhanced strength, and so on. These machines can produce interlocking bricks like legos which can in turn have molds customized. They are usually dry stacked without rebar, with grout placed down the "cores" of the bricks along with steel rebar reinforcement.
Well, what if we had something like that? It could require a curing process, so still have the potential for environmental damage (or sun baking which takes longer) but then players can customize a lego type building system.
It could be as simple as drawing shapes on a mold piece, which translates to how the block is made and how it matches up with other inlocking blocks.