One obvious thing when looking at the Chinese laser is that the table to hold the workpiece is an unnecessary spring loaded contraption that limits what you can work on to 209 X 88mm. Why? Removing it reveals enough space to add a table measuring 350 X 230mm. It’s easy enough to trim the end stops so that the laser head can cover this area too. So on to making a more useful lasering area!
I started with some 10mm L shaped aluminium, cut some 90 degree notches in it so it could be folded into a rectangle. I made up some corner pieces to hold it in shape. These were initially 3D printed but I ended up CNC milling them from 5mm acrylic instead. The L shaped slot held the aluminium frame firmly and hex cutouts underneath held some M6 nuts. Some coach bolts provided simple height adjustment.
It was all finished off using some aluminium honeycomb (6.4mm cells and 10mm thick) from Easy Composites.
In the future this could be motorised, but for now this is all I need to cleanly cut sheet material up to A4 in size.
0xFRED 
Does it hold horizontal at the center of the bed, or sags? (I’d like to cut paper and other soft materials and sagging ruins it)
It’s only supported at the edges so does sag a bit. I’ve cut paper without a problem, although that’s often been a test for fit before I repeat in acrylic so I’ve not been that particular. Then again, I’ve done some nice cards too. It would be easy enough to add some cross members under the honeycomb if needed.
How did you dxpand the honeycomb? Did you use a row of nails at each end as easy composites suggest?
One thing I do not understand is how this method will deal with the cells getting narrower as they expand.
Also did you cut the honeycomb to size before expanding it?
I just expanded it carefully by hand. You’re right that it gets narrower as it expands. I can’t remember if I allowed for this or cut it afterwards.