I did exactly this about 4 - 5 years ago I bought spring-based (not electric) height adjustable legs / frame and then went to home depot with a friend and cut

I did exactly this about 4 - 5 years ago I bought spring-based (not electric) height adjustable legs / frame and then went to home depot with a friend and cut a 70" x 30"ish x 1" piece of wood. Added a rounded edge to one side, sanded, stained it, then screwed it into the frame. I love it. It's huge compared to a typical desk, and although I haven't done anything unique with it, it's been solid. I dont really know what I'd add to it that would be worth giving up desk space, tbh. The conveniences / tools I use work fine being on the desk rather than part of the desk