You don't move forges. You set up a portal to a distant area so you can unload non-metal stuff and rest/get new foods easily. Then start mining and bring it back to your main base via loading up a boat full ideally. Karve only has like 4 storage slots but longboat has many—this is why building your main base along an ocean shoreline is strongly recommended.

You can also make use of carts but they are a bit underpowered imo.