accurately measure the wall lengths, heights, doors, windows and use the cutter to make the walls. the floor plan outline pasted on the wood is mainly a guide, (but will also show layout details once the model is complete) measurements are best taken from the dimensions provided on the elevations and floor plan.
the edges can be square but are best if sanded at 45 degree angles to butt up agains neighbouring walls, heres the nephew sanding away.