From memory (been ages since I've had one apart) it is very fiddly, however:
The dogleg bit of plastic with the square on one end - the square end goes in the square hole under the button, and goes inbetween the cyclone assembly plastic (which from memory is the fiddly bit as the two cyclones meet here). The other piece of rounded plastic goes under that further down the bin, and pushes the bottom flap out (round end to round end on the plastic bits)
Sprin wise, the long spring goes just under the dogleg square, but rests on part of the clyclone housing. The shorter fatter spring *I Think* goes over the very bottom of the pegs by the release flap, so it pulls the peg away from it when the button is not pushed.
Best thing to do it try it all without the springs and check it works, then put the springs back appropriatly. Not got a DC11 to show you pictures of it all together I'm afraid.
Good luck! Did you wash the cyclone out? One of the best things you can do that is, high pressure hot water is ideal, but even a long soak and a good swirl around in a bucket of water will sort it out!