The only thing looking off to me are the two boxes in the middle row. On the right one I'm not sure about the topright border of the cutout piece, it seems too unparallel to the outer line of the main box (I hope you understand what I mean :D)
On the left one, there are those two parallel lines on the right side, I guess it's again sth cut out? But that doesnt appear that clear.
But other than that the cut out pieces look fine to me! And the outer boxes are nice as well.
How are you liking perspective?