Have the plywood cut to size (we cut ours to 1800mm wide x 1200mm high). Set up a mitre saw with a stopper to cut lengths of dowel in half, cutting three lengths at a time. Note the dowel is slightly longer than 2.4m, which allows for the width of the saw blade.
Tip: Using 12mm-thick plywood as the backing for the dowel keeps it lightweight so it can be constructed on a flat surface, then moved and attached to a wall using fast-drying construction adhesive.