Fairphone actually has limited choices here. The tricky thing is the battery in the phone which EU law deems as an “hazardous good” (read: it can bloat and explode). I think this rules out slower shipping options, at least for all shipments including or solely consisting of a battery.
As Fairphone has actually made some progress with regard to reducing the air freight share of their delivery chain (China factory → Tilburg warehouse in NL), I recently suggested further options within Europe here: