Next project The Goddess sword from the legend of zelda skyward sword.
So,
stage 1 - create a base shape, once again this acts as the base for the entire prop every thing you make will correspond with this base.
Stage 2 - with the base refined and complete, create full copies of the base If required. ( for this sword i used 3 main layers, so thats 1 for the base, 1 for the top and 1 for the bottom, i also added two strips for extra strengthening.)
Well in the UK, its used to make "For sale" signs for houses etc, you may be lucky to find the same material where you are, if not, im not sure where you could find it. sorry i cant be more helpful.