This is why HN is special!
I guess a lot of stuff happened over the phone? If you write a document, how do you send it to others? Did he use a fax machine, maybe?
He had a Palm Pilot he would scribble on a lot to work out of the house when those became a thing, and he had one of the first actually-portable laptop computers. We (he involved me in a lot of his process of learning tech) tested out early tablet computing devices (running Windows 3.0 "for Handwriting" ;P).
-Design jobs like architecture and drafting
-Small device repairs (where the device is high value and can be mailed)
-Creative labor like copy writing, editing, etc
Also, where I grew up in rural Montana, a lot of jobs that are considered to require an office but which can be done over the phone were worked remotely up until recently. Sales in many industries was done over the phone with people stationed throughout the Western U.S. states, each managing about a 100,000-300,000 sq mi area.
I'd typically do a short dialup call in the morning and one in the evening to upload emails I queued up to send, download any emails I received and sync up code repositories.
Honestly I often wish for similar conditions today (except the 2400bps part!). The productivity and mental peace of zero distractions all day long was so much better.
As to how to work? No different from today really. Sync up the code repositories and do all development locally for the day. Or work on architecture/design documents.
I sometimes seek that peaceful working condition by working remote at locations with no signal. Wish I could do it more often.