How i preserve features that i made after i clicked FLAT PATTERN ?

Hi Leon

My advice is mostly relative to Inventor but I am 1000% that you can pick the same way to solve your problem... in solidworks as well.
(Check the attached)

So, what you need to do is to find the command that actually "unfold" the bending part without being in the flat pattern mode then you can apply your
cut out features "fold" and keep these in the normal state...

Just be aware that the unfold command unfolds only one bend at the time...
Flat pattern unfold everything...

Regards

Ioannis

P.S.

I hope that I didn't misundestood anything ;)

Try this link
http://grabcad.com/questions/how-we-are-making-flat-pattern-in-ug-nx-7-5-from-solid-model

http://www.youtube.com/watch?v=Gr2_tuDNRvs

I thing this is what you are looking for...