My first attempt was a complete failure, but this one turned out ok. It's important to only glue the top of the petals together, otherwise you'll end up with a pretty little flower-ball that won't look as impressive in your card. ^^ It's also a good idea to not use card stock for your flowers... :D Had to learn the hard way. :P
There are a bunch of videos on youtube that describe the whole building-process. I tried searching for <pop up flower card> or something and that helped in solving my little problems. :P