How to create a smooth surface onto a rectangle frame? Ok, so I am modelling a surface for a mac book pro, and I realized that it looks kind of "unrealistic". It seems to me, that apple used some trick to achieve that surface. It seems like a smooth rounded surface inside a rectangle form...

I tried to achieve this with extruding and model according to a background pic but that didn't do the trick. 



What I felt like would be the closest to the original was to go into proportional editing and just pull a certain amount of vertices out. But that looked like as seen in the pictures. 



Maybe someone can give me a hint if I am doing something wrong. I want to have the "frame" sticked to the grid and then just have the rest of the vertices to move and form the smooth surface...

U can see in the pictures what I did and what I want to have but smoother... Maybe u get an idea

Thanks for your help. 

Greetz
You could use the bevel modifier to create the rounded edges on the unscaled standard cube.

Add an edge loop Alt-R in the upper part and delete the bottom vertices.

Select the beveled part and scale it along the z-axis S,Z
Note that you shouldn't scale the object to align it to the original model because this would distort the edges. Use select and grab instead.