I made my (wall-mounted) desk with two stair treads: https://www.homedepot.com/p/EVERMARK-Stair-Parts-48-in-x-11-1-2-in-x-1-in-Unfinished-Pine-Plain-Cut-Engine

I made my (wall-mounted) desk with two stair treads: https://www.homedepot.com/p/EVERMARK-Stair-Parts-48-in-x-11-1-2-in-x-1-in-Unfinished-Pine-Plain-Cut-Engineered-Stair-Tread-8503E-048-HD00L/202087175 https://www.homedepot.com/p/EVERMARK-Stair-Parts-48-in-x-11-... One tread for the top. Another tread cut a bit shorter and used as a keyboard tray. I've been using it for 5 years and am happy with it. But it's only suitable for computer use, not for dealing with physical paperwork or handwriting.