Very basic,but effective...
Take two sheets of 12"x12" liteply, coat one surface with 24-hr wing skinning epoxy.
Lay them against each other with their grain layers at 90 degrees to each other.
Coat one outer surface with epoxy, and lay on a layer of 200 gram glass cloth. Stipple the glue through the cloth with a stiif old 1" paint brush.
Lay this face down on a square of melamine faced chipboard, or similar, with a layer of thin black polypropylene as the separator (I use part of a new rubbish bin bag--really!)
Repeat on the other side(which will now be on top)
Clamp around the margins of the two outer boards with as many G-clamps as you can, or weight them down on a strong bench with as much weight as you can(2or3 old car batterries works OK)
Excess epoxy wiil squeeze out of the sides of the sandwich -just make sure it doesn't go on the carpet, or anywhere else to get you into trouble with the civilized members of the family!
Leave somewhere warm for at least 48 hours, and then it's done.