I did, but it's not pretty or workmanshippy. Not a heirloom piece. Cheap, though; unfinished pine (1.5" x 3.5", roughly, from memory) legs, lapped cross members, bolted together with M10 bolts (I think...3/8", roughly), with a full sheet of 22mm MDF (3/4") ripped lengthwise and glued together, doubling the thickness, with a few pine cross beams across the width at strategic locations (have three sets of legs) stiffening, and a melamined chipboard worktop. Also a shelf just off the floor, resting on the bottom cross beams, and another higher up, resting on s'more heavy lapped and bolted cross member, and some pressed steel angle brackts for the middle bit where I didn't want to waste storage space. It's also bolted to the wall, because the shop's tiny, but even when it stood free it was pretty rock solid. With two full sheets of MDF, it's HEAVY. Only thing I would've added would be some length-wise members if I wasn't bolting.
Picture:
It's a bit of a mess, and is about 1/3 of the total surface area of my tiny shed shop, but it has a number of advantages: it's cheap, easy to clean, nothing much sticks to mealmine (glue-proof, pretty much), I can drill holes in it for fixtures with gay abandon, and if the top gets too beat up, I'll simply replace it with a fresh sheet of melamine at minimal cost. I'm going to be installing a router in it permanently at one end, have also made a small plug to plug the hole when it's not in use so I can still use the surface for other things. Only thing I need now are some longer (3/4" to 1" long) countersinkable 1/4-20 machine screws, which I can't find locally...
As for flatness, it's stayed pretty well put, and you want to check it with a straightedge. Which is an abosultely essential tool if you're building guitars. It doesn't really need to be perfectly flat across its entire length, just as flat as possible. Mine's sagged a tiny amount (I estimate about 0.5mm over a 1 meter span) along it's length, between the legs, not at all along the width. Then again, I'm not sure I can expect much flatter over these spans from MDF.
