12:31 PM, Sunday July 19th 2020
the diagonal lines from your "cube" that you connect to the horizon are faced away from your Vanishing Point (VP). You are suppose to align it with the VP as you were with the plotted perspective, but in the rough perspective instead of drawing a visible line from the corner of your cube to the VP, you just need to plot a small dot for indication, aligning that dot as best as you can with the VP as if you were using a ruler like in the plotted perspective.
if you had a hard time understanding the plotted perspective, I suggest you read the material again and when you fully absorbed it you won't be having a hard time with the rough perspective, because they have similar steps just without the use of a ruler and not having visible lines to guide you.
it's hard explaining without showing visuals but I hope this helps you even just a bit.