Firstly, take a good look at the top photo. The cross pieces both go under one middle spar and over the other one. Hence the kite can be opened out into a box shape.
Another 2 cross pieces need to be fitted now, to make the kite rigid. However, due to the inexact nature of working with bamboo skewers and plastic, you need to fit each one individually. Here's how...
The bottom photo is a close-up, with my markings visible on a main spar and one of the cross-pieces. The other cross-piece had single marks instead of double, to tell them apart. Hope you get the idea!
All this is visible in the above photo. At this point, you've pretty much finished making the MBK 2-Skewer Box Kite!
Now, I had some trouble with the cross-pieces falling out while the kite flew in rough air. Hence you might like to glue the cross-pieces in place! The kite is a convenient size to put in the car, fully rigged, and won't take up much space in a shed.