I've made a standing desk that mounts on a tree.
It's held by a strap that fits snugly around the trunk. The table is stable, and I work on it all day. On a hot day, a tree give me a cool shade; on a colder spring day working standing keeps my blood circulating and I'm warm. It's a win-win. And, I'm "enjoying the lockdown" by working outdoors instead of the sterile air-conditioned environment of the office.
The Tree Table is now on INDIEGOGO and you can support the project and get your own Tree Table when it's ready.
https://www.indiegogo.com/projects/tree-table