One P.S. to the post. 
It might also be an option to first cut the pieces from the first 4mm sheet, then the second and then just laminate the smaller pieces instead of the whole sheets.

When I've needed to glue sheets together, the steps I've taken to get a successful result are...

Use cauls: a truly flat surface below (I have a very flat 4x8 bench), and a sheet (or three...) of 3/4" particle board on top

With a roller, wet the two mating surfaces with neat/straight epoxy, wait a couple minutes, and wet again

With a toothed trowel, spread a mayo-mix of epoxy, thickened with cotton flock, microfibers, or even wood flour.

Marry the two sheets, add the upper cauls, and load whatever weights are available: tools and tool boxes, paint cans, workout weights, etc. Try to distribute things across the whole surface.

If you've run a strip of packing tape below the lower sheet's perimeter before all this, the squeeze out can be sorta cleanly scooped away from the edges, and your bonded sheets will be free-able from the lower caul/bench.

A benefit to gluing big sheets is that the cauls can be used full size, and can just be put back into the storage rack when done. Also, the squeeze-out and edge-bleeding happen at the 4x8' edges, which are always cut away when cutting out parts.

   Thanks. It was a bit of my plan to use some sort of cauls, since I do not have an endless amount of clamps at hand. 
So no glass should be used? Just thickened epoxy? 
 

No glass.

First, it would be added as the meat in the sandwich, also known as the neutral axis- the part of a bending structure that contributes nothing to bending strength. It would also require lots more resin to fully wet and fill the glass weave so that there is still full adhesion to both surfaces- you don't want the wood riding on the weave texture's hill tops, without full resin contact. More weight, lots more expense. Lastly, if using templates and flush trim router bits to trim your parts to size, the middle glass layer tends to wear a dull spot in the cutter...

   Thanks! That makes sense.