  We construct a (lax) Gray tensor product of $(\infty,2)$-categories and
characterize it via a model-independent universal property. Namely, it is the
unique monoidal biclosed structure on the $\infty$-category of
$(\infty,2)$-categories which agrees with the classical Gray tensor product of
strict 2-categories when restricted to the Gray cubes (i.e. the Gray tensor
powers $[1]^{\otimes n}$ of the arrow category).
