This was borne out of a sore back. Our table was far too big to move about so my wife was always bending over the table to use her laptop. After searching around to see what timber I had I decided on this. The tabletop lifts and cantilevers forward over her knees while sitting on the couch, the laptop is now at a workable height for her.
The dimensions I used are purely due to materials I had and the height of the knees I needed to get over. For this reason I am omitting to restrict people to my sizes. Almost any size will be correct.
So, main body and legs are 12 mm mdf. Top is 25 mm mdf. Underside is plywood and inside is 1/4 ply with dowels and string. I used hardwood strips for the dowels to rotate in as they are more robust.

Step 1: The Carcass

Being just 12 mm thick I decided to double up on the main frame. So I laminated the legs and frame to an inner frame the was about 20 mm up from the bottom. This ment that the ply underside was above flush. For the legs I placed some 50 by 50 mm shaped inside to strengthen them as the mitred edge joint would not be strong enough either. I left them 2 mm proud so that they would be on the floor and not just the mdf.

Step 2: The Cantilever

The swing of the cantilever and the weight of the top was just too much pressure on the wood and dowels alone so, after gluing and clamping the dowels to the plywood, I whipped the string tightly around all four ends. The dowels rotating inside the hardwood straps of the cantilever frame was noisy to say the least. My cats were watching for the mice to jump out, it was that squeaky. Candle wax to the rescue. So versatile that stuff.

Step 3: The Top

Having finalised the size of top I was going to use I planed the edges all around to a softer bullnose. At this point I laid the top face down and placed the base on top to fix them both together. I routed a channel along the front for a finger grip then fixed the plywood underside in place.
I gave it two coats of primer and two top coats of colour and so far one of clear varnish. I added some kitchen door soft close fittings that are like little air buttons and this served well to give the lid a quieter closure.
Job done and works a treat.