You setup model on a table - so that you can stand behind it and see at eye level, the trailing edges of both wings.
centered.

The sunlight or lights should be centered on fuselage -if possible
looking from one panel to the next -back and forth -you will see even very slight differences in shadows and highlights
any differences should easily show themselves
especially the hinge line
This takes a few attempts at getting lighting you like
a lot of light is NOT required -just try to center the light source
any diffrences in thicknesses - hinge lines - warps all become obvious.
Those silly levels will show differences -or NOT show differences if leading edges are not identically shaped
hinge location will also trick you
Learn this procedure and give the Robarts to the children to play with