I'm trying to build a TV stand which will have a top on it about 80" x 20" x 3/4". It can be thicker than 3/4" but I'd like it to be at least that. Assuming I build a supportive frame, what's the cheapest way to get a piece that fits the bill? I've looked at using plywood and edging as well as biscuit joining planks together, but would like to hear other ideas.
A narrow slab door might fit the bill. 80" is a very common height. Architectural recycling places, such as Habitat For Humanity Restores (if you're in North America) have them for nearly nothing. If you get a hollow core and it's too wide, be aware that it's a bit fiddly to make it work well.