In the never-ending quest for perfect ergonomics, I hacked together wrist rests to attach to my computer chair and set my keyboard on. The end result looks a bit like the captains chair in Star Trek.
Prior to this, I had installed a keyboard tray on the desk, but I'd bump it shut with the chair arms and would end up leaning far forward to use the keys, aggravating my shoulder and neck. These move the keyboard right under my finger tips, with my elbows firm against the chair back and my chest and shoulders open.
I decided I could build these myself with scrap plywood. I prototyped it with some cardboard, took some measurements with a digital caliper, and did most of the cuts with a circular saw. I don't own a scroll saw for some reason, so I ended up using a saber saw to do the fiddly bits. I ended up cutting off the wrist rests on my homebrew Dactyl keyboard to get the halves positioned correctly (don't worry, it's easy to print replacements).
One really nice thing these let me do is type while I lean all the way back in my chair, taking some pressure off my lumbar. I added the second layer of plywood as my wrists hurt a bit after the first week.
This does mean I need to "buckle myself in" - the 3.5mm cable stretches across my lap - but I've been meaning to try a fully wireless split anyhow, so this might be the rock in my shoe I need to get that project started.