The puzzle joints are tight.  Mine required a fair bit of pressure and a rubber mallet to get them all together.  I used 3/4" plywood under each joint, on the floor, so I could get medieval on it.  Up on a 1/2" plywood on horses, it bounced and flexed.  The ends of the planks were propped up to the same thickness with scrap pieces because I didn't have a single big piece of plywood.  The thick plywood is convenient to screw into for clamping also.  

   If you add a couple of 4x4's on top of the horses and under the ply, it will give you a very stable surface to work on.  Get the straightest 4x4's you can find.  And I used 3/4"  2-sided melamine instead of ply, as glue, epoxy, and paint tend to wipe off fairly easily.  The weight of the melamine will hold the 4x4's in place, making it unnecessary to fasten them down.  When you're done with the project, everything comes apart and is easily stacked against the wall in your garage, ready for the next time and taking up little space.

I put my aluminum extension ladder on two horses and then 1/2 inch ply on top.  Very stable and flat.

Oceanlluvr,

This link might be of interest.

http://www.clcboats.com/forum/clcforum/thread/32362.html

Cheers,

Dick

   Essentially it don't matter how you do it as long as it provides a stable,. flat  work space.

Take a look at this video.

https://www.youtube.com/watch?v=pwmAQzUta88&index=3&list=PL8E4DB9EC74DA8888