ok once youve got all your pieces cut and under coated its time to start building ..
(make sure you build it were you are goint to grwo as if you make it to big to go up the stairs you will be taking it apart and building it again)
i recomend you pre drill your holes as you are so close to the edge of the wood ..
on this box iv used mdf coner brackets for extra support ..pic(1)
start by screwingall sides together ...