The cube as 4 tabs : #1 being the lowest and #4, the highest.
Wateright plugs are always found between Tab #1 and Tab #4.
Screw G2 connecting pin, sliding nuts on lowest tabs.
THE SCISSOR TECHNIQUE
While assembling bigger sections on water, place a G2 CONNECTING PIN, as shown on the picture.
Then bring the two sections side by side while making sure that the tabs properly overlap each other. Then insert the missing pins. This technique will help you assemble big sections with ease