If replacing just the AC evaporator and accumulator, and not flushing the system, how much oil should be added before putting back the refrigerant?

The AC system was evacuated and opened to remove the evaporator box so I could add some missing foam sealing. And while the evaporator box was out I figured it was a good idea to replace the evaporator. But otherwise the system had no leaks and was working fine, which is why I'd like to avoid flushing it and messing around too much with the compressor.