Please show the frame which holds the plate in the preloaded state.

Please explain how the plate is loaded when it is bonded to the frame.

Please show how the frame is connected to the optical bench.

You would use a multi-step Static Structural model where step 1 is applying the load to deform the plate to a shape, step 2 is bonding the plate to the frame, step 3 is removing the load that deformed the plate, step 4 is to change the direction of gravity or mount the frame to the optical bench.

If there is an optical prescription for the surface of the plate, then the deviation of the surface from the prescription can be measured at each step.