following the stop motion videos on goran's site gave me the basic idea of a square grid and repeated pleats running the full length/breadth of the paper. but frustratingly i couldn't find any detailed information on the technique or folding patterns, and my first attempts were close, but clearly not right. then i stumbled upon a diagram in robin scholz's flickr stream and i was away.
in his TED talk goran mentions that it took him ten years between folding his first basic leaf and discovering that there was an additional fold he hadn't realised was required. this locking fold along the edge stops the pleats from fanning out and creates a much tighter, more curved shape. the bowl above is made by pleating the basic pattern from two diagonally opposite corners and then locking the edges.
fortunately i didn't have to wait so long to find out the secret of the locking fold. this style of origami is also known as pureland (because it uses nothing but valley and mountain folds, none of the complex twists, pleats or sinks required in origami tessellations) and with that search term i finally turned up a paper (pdf) that explains the basic structures.
now i have them down i'm looking forward to more experimentation.