I build an outpost in each biome and when I reach the swamps, I use those indestructible trees to build a safe outpost for processing my Iron...

Those trees act as "grounded" so when you build up in the tree, any parts that touch the tree are blue, making it possible to build entire base up there.

Here is an example of one (not so high) in a tree, but inside this outpost I have smelter and coal kiln and fire hearth etc.... up out of harm's way... The fence below is just a safety measure to protect the stairs leading up to the outpost.

https://steamcommunity.com/sharedfiles/filedetails/?id=2643987509

https://steamcommunity.com/sharedfiles/filedetails/?id=2643987894

https://steamcommunity.com/sharedfiles/filedetails/?id=2643988771

I find it far easier to gather my iron and bring it here (at the source) rather than trying to ship it across the map

PS this is vanilla, no mods