I like to hike into the middle of the wilderness and work, which means I want as little weight as possible.
Initially I was thinking I'd buy one of these: https://www.intension-design.com/tripodtable
But it is both heavy, not versatile, and expensive. Instead, I made my own:
1. Got a high quality, lightweight camera tripod with a ball head which I could use for photography anyway. This is more expensive than the above but extremely lightweight, durable, small and w/lifetime warranty: https://www.peakdesign.com/products/travel-tripod or https://www.amazon.com/gp/product/B085BQS6K4 the important thing here is that the ball head can be well-tightened since you'll be resting both laptop and some weight from your arms on it.
2. Got an HDPE cutting board (you can buy these anywhere for like $10). This acts as the 'desk' surface and is very lightweight and durable.
3. Drilled a hole in the top two corners of the breadboard, through which I passed and knotted 1/4in bungee cord. This crosses along the top of my keyboard, below the screen, in the hinge of my laptop and keeps the laptop from sliding off. It's a bungee seatbelt, basically.
The whole thing compresses down to minimal space inside my backpack, so that I can also fit a lightweight backpacker's chair if I want to sit – but the beauty of the tripod is that it also adjusts for standing height, and I've found I don't even bring the chair anymore and just stand there in the middle of the woods writing. Good for posture and productivity, and when I really need to rest I also have a hammock that I can string up :)
I really like this tripod + breadboard setup a LOT and I even use it around my house now.
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EDIT: photos as requested
Laptop strapped in: https://ibb.co/yNgbtRf
Underside: https://ibb.co/ZhpxdYg
Top w/out laptop: https://ibb.co/rbs2bVK
Mounting bolt: https://ibb.co/5W9BvCH