Trying to MAP drive to work on the NAS from HOME


I am trying to setup a connection for my boss to connect to our NAS at work from home.
He wants to have it Mapped like a local drive but from home, so we need to setup a like-local connection from PC to our work network.

As I understand there is definitely a way to do this, but what I am a bit lost with how… there so many methods and manuals its confusing as to which is services we absolutely require to get this going…
Between Port forwarding, DynDNS and VPN, WebDAV, not sure which ones I need to use.

I have forwarded the ports for WebDAV and downloaded the client, but get a bit lost with where to go next.
Can someone break down the method for port forwarding to setup for a home pc to connect.

Do I have to create a static IP for the home PC, and then forward web-dav ports to that IP ?

Any help from someone who has done it before would be awesome. I’ve got a lot of manuals and stuff I just need someone to breakdown the process… and what is actually important when setting up this kind of connection?

We have a Static IP address at work.
The Home PC would probably have a dynamic one being a home service.

Do we just set the IP on his home network or do we need dyndns ?