Basic modeling question.

 From:  sandykoufax (JEONGHO_KIM)
1530.1 
Hi, all

i'm newbie. :)

I'd like to model below phone.

but I don't know how can I make the case outline.

At first, I start drawing outline at top view.

and then, copied several and moved it upper and lower.

but I found that the top plate is not flat.

How can I solve this?