OK, the pressing is clear for me. thanks for your comments.
The next thing I'm not sure of is the cutting of the canvas.
In Barb's book it says:" cut two pieces of canvas of these dimensions, with the length parallel to the straight grain of the canvas".
Allas...my English is not sufficient enough, what does this mean?

I have a piece of canvas that is very bendable in one direction, in the other direction it's very stiff. How should I cut my piece?