For laminating 3 pieces of ply, Screw them together on a table when gluing, drywall screws work good for this. A jig table is a heavy piece of ply, with a strip of wood at both ends for rocker. Just screw the pieces of ply to the table and let the glue set, remove the screws fill the 1/16 in holes, shape and your done.
This method works better than vacuum bagging for shaping ply, no bricks, pressure constant and you can adjust the rocker shape when laminating.
What size of board are you making? Most larger ply boards do not need rocker, and rocker actually decreases performance of the larger ply boards. With 9 or 10 mm ply the ply flexes when riding, dynamic rocker.