Armos have appeared in many Zelda games to date. In Wind Waker, the best strategy to defeat them is to shoot them in the eye, paralysing it and enabling Link to attack the gem on their backs. Link can also sneak around the back to attack their weak spot.
Tips: Build from the top down. Take your time when gluing the smallest parts, and wait for the glue to dry before moving on to the next flap. After testbuilding, I found it easier to stick on the spikes without flaps. To do this, just apply a small amount of glue to edge you want to stick and if you use PVA glue you'll find it will attach quite quickly and easily.