Basic Perspective With David Hohn

hi Guys. Basic Perspective assignment 3 part 2  "Draw a cube and practice duplicating it in perspective to serve as a unit of measurement."
I am totally lost at time stamp video from 10:30 when David is explaining how to draw a cube and copy it multiple times on the grid. his example is draw a square that is 2 squares wide ad 2 squares tall. then repeat that on same row or horizontal grid line either side  i still don't get squarecubes. i get rectangular cubes. how do i correct myself when you see this work i have done.
i used 3cm wide. tracked across the grid horizontally. struggled to eyeball the height depth from the top to create foreshortening that is in perspective. i want to practice this but i don't know if i am doing it the right way. thank you

On the photo, we get the impression that the width and height aren’t the same though. Are they?
Otherwise, I think you are doing it the right way. Remember that the linear perspective rules are an approximation compared to how your eyes actually see the world. For instance, the more your cubes are away from the vanishing point, the weirder they will look.
In terms of the depth, it is a guess that you have to make. If it looks good, it is good.
But you could also recreate this scene in Blender, and see how it looks like. Although, it will look different depending on the camera lens. 
@GeoffreyMégardon Thank you Geoffery. i think i'm confusing myself and worrying too much about what good looks like when i compare what i see in the tutorials. i guess it's because i want to know i am practicing the right way. i'll keep on working on this no matter how long it takes.