Okay, I've been using a computer desk from the 1990s. It's obsolescent, but I haven't found anything better to upgrade to, because I'm not sure what qualifies as an improvement.
To understand my setup, picture a flat desk. Now, put a raised monitor shelf at the back of that desk. Then, flank that monitor shelf with some taller shelves at the back.
There is a keyboard tray under the desk itself.
You can see that it was designed for CRT 4:3 screens, not large wide-screen monitors. So now I have the monitor sitting forward on the desk itself, rather than on the monitor mount at the back of the desk.
Anyway, the biggest issue for me, ergonomically speaking, is that the keyboard is safely in a below-desk tray, where it poses no ergonomic issues, but the mouse is on the desk itself, above the keyboard tray. It's on the desk because:
1. It can't fit on the keyboard tray, since I have a full-size keyboard there.
2. The armrests of my chair at the sides would get in the way of using a lower-positioned mouse. [They're designed for use with a desk-positioned mouse.]
Now, I doubt that this is the best ergonomic arrangement. The mouse should probably be on the same plane as the keyboard, right? I actually have the keyboard tray tucked into the desk somewhat, so that's it's almost like a 65% board [the F-keys are hidden under the desk.] This is a usable arrangement, but I am still leaning forward to use the mouse.
I guess I have two options:
a.) Put everything on the desk. This would probably necessitate moving the monitor back, though, and getting rid of the shelves that are in its way. And it would necessitate a smaller keyboard. At least the chair arm-rests would be aligned with everything.
b.) Put everything on the tray. This would also mean a smaller keyboard. And I would need a chair with adjustable armrests, or no armrests, I guess.
Or, I could get a new desk. But for what ideal arrangement, I'm not sure.