I've been doodling with a piece over at DJCA about calculation and as part of that task I watched a few YouTube videos about how to calculate. Almost none of these actually tell you how to calculate, although several do show you.
Here's one for you to think about from Black's point of view:
Some time after writing the piece about checkmate patterns, I bought V. Vukovic's
famous book The Art of Attack in Chess. In it he
gives a chapter full of mates, shown below; the numbering and
terminology are his.