I work from my home office.

You may have a home office meaning that you have a room in your house that you work in. However, the context that you have described (re; "the pandemic") you would say "you are working from home" or "you work from home" as it is not your usual place of work. Not only this, the work is nothing to do with the room. You could be working in your kitchen, bedroom, etc. but it doesn't change the fact that you are working in your house/home. I hope this helped but if you have any further questions, please feel free to get in touch www.italki.com/maddie

"He has his spare bedroom set up as a home office."

One could also say, “I am working remotely (from home). Others say, “I telecommute”. Simply” work from home” is the most common and clearly understood.

work from home