Somehow this video is missing the part where is shows the actual foam-crete structure inside...
But anyways, this kind of non-autoclaved foam-crete is very easy to make. Basically you only need cement and aluminum powder. The powder reacts with the wet cement to create gas that bubbles up the cement.
The main problem with this is that the result is very weak. So you either need to make some sort of ferrocement sandwich structure or cut it into smaller blocks to autoclave it for extra strength. The latter process is quite energy intensive and needs a large pressure vessel, but those autoclaved foam-crete blocks are quite commonly used as building material in Europe.