Belgian linen is stretched for me by Schweickerdt. They also make the board on which I work and prepare it with gesso.
I prefer to work on both canvas and board as each has its own character.
Large canvases have to lie flat while they dry.
Generally I don't work from sketches. I start with a charcoal drawing directly on the canvas or board and start playing as soon as I am satisfied with the drawing.
Between work sessions time passes while the artwork rests.