Yep, get 90% contact by moving your glue around with a toothed mastic trowel, notched piece of plastic laminate or whatever. 2X battens with the crown towards the ply and clamped at edge; yep, that's good too. One other possibility is a plywood "torsion box". This is basically a frame skinned both sides. Let's say you use plywood for the frame, maybe between 1" and 2" rip. This plus 2 skins of 1/2" ply would give you a benchtop 2 to 3" thick. If you are careful with construction of the frame (2 studs, ribs and plates on 16 or 24" centers) and you make sure that any crown in the skins is opposed (crown up both sides), you should get a fairly true surface which might end up a bit lighter than the double plywood laminate. A torsion box panel with four legs will maintain it's rigidity such that three will touch the ground and the fourth can be shimmed up. Very little chance of it twisting when it's set on uneven surface or ground. Another .02 worth.
I see now that you mention cutting "final pattern" which I take to be cutout for shooter, so perhaps this is not the very best idea unless you build the frame to match.
jack
