Once we have our big and strong plywood ready, we start to make a carton stencil of the shape to make sure that we have exactly the same shape in all of the steps.
Then we draw it over the board... but we make two stencils one for the right and one for the left... so we can alternate them and minimize the waste of material by puting one "inside" of the other.
We use a jig saw to make the cuts... dont forget to calibrate the angle of the blade and be patient 'cause some times the blade make a non desirable angled cut insted of a clean 90 degrees angle. Take it easy and practice... you can also draw the steps whit a 3/8" space between one and the next...this gonna be very usefull in case you need to rectify some cuts. (So dont be afraid to make a mistake...we can always find a solution)