Morning AA,pics below are of a single box I bought off of E Bay so I could copy the pattern and see what bits I needed.
All I did was increase the measurements on the width and depth by a third to make the double.
You will need 1 sheet of 9mm ply
1 sheet of 5mm ply (try builders merchants mine are cheaper than b+q etc)
some no nails adhesive
panel pins
1"1/2 oval nails
hinges
latch
nuts,screws,washers and carry strap
dimensions are width 450mm,hight 200mm,depth left 365mm,depth right 23