Failing that, a door with one edge rested on a radiator and the other a stack of cardboard boxes.
I work from a proper ergonomic office desk now but it beat many other alternatives including a dining table and various purpose-made 'home office' desks.
(Accepting I got lucky with the height of the radiator).
In the same vein I worked off a folding table for a long time. It was cheap, large, and surprisingly sturdy. If I needed the room it took up back I just folded it away.
If you live and work in Denmark, your employer is technically responsible for providing you with a height adjustable desk, chair, keyboard, mouse and monitor, if they expect you to work from home.
Working from home is not an excuse for the employers for allowing you to work in an un-ergonomic environment.
Finally getting around to getting a proper desk/chair/monitors really made me enjoy working from home a lot more. I don’t do it terribly often, but I really feel like it makes me more productive.
Also working with a remote colleague who doesn’t have good webcam/microphone/headphones is an absolute nightmare. I’m sure most of us have had colleagues that were frustratingly hard to communicate with remotely, and I’m sure most of us have avoided communicating with them because of it.
I work from a proper ergonomic office desk now but it beat many other alternatives including a dining table and various purpose-made 'home office' desks.
(Accepting I got lucky with the height of the radiator).