I have the same exact question... my sister bought some of these in a GB and gave me 3. I took one apart and it's now a hot mess.
The center does not come out easily as you know- layers of plastic dividers and it just totally fell apart when I was done removing the plastic dividers and stem and now I can't get it back together either.
Do we use all of the flower layers when we put them back together? Or are some left out? The finished flowers I've seen are so pretty... how do they get that way?
Sorry I can't help... but hopefully some other ladies will come to our rescue.