How to make curved (bent) rectangle, and add material? This question has two parts.

• First – I'd like to know how to make a rectangle with a curve on it. Don't misunderstand me, I DON'T need to know how to make a rectangle with rounded curves. I want the actual rectangle to be curved. See the screenshot below.

• Second – Once I get that rounded rectangle, I'm having problems with making a material go along the curve. Again, this will be explained throughout my question.



Here is a mockup of what I want.





The Curve.

As you can see in this image, I have a rectangle curved along the top/bottom faces. Its corners are not rounded (meaning they look sharp), but the rest of it is smooth. It doesn't look like a bunch of small rectangles (like it would if I merely subdivided it), it looks like a rounded rectangle. A curved rectangle.



The Appearance.

Also shown in the above image, the corners are colored black. The mass-majority of each of the faces is a grey color, but the edges are black. I would think it's a simple task, but I'm still beginner at Blender.



What I Have Tried.

I have already tried making a curved rectangle, but I'm having problems making it look smooth like I explained above. Applying a "Smooth Shading" makes the curve look smooth, but the edges aren't sharp like a normal rectangle. I have tried applying a Bézier Curve, but that is a little complicated for my limited experience. All the tutorials I can find are either irrelevant or unhelpful.

As far as the material, I am completely stumped here. I can't draw it on, because it turns out looking horrible. I don't know how to work the "UV Editing" window. I have looked for tutorials, but they are again unhelpful.



What Do I Need?

I would appreciate a full-length description. Maybe add in some screenshots (gifs would be amazing!). OR, I would also appreciate some links to tutorials that would help me. Like I already said multiple times, I can't find very much on Youtube. Some help would be appreciated.

Thanks for any tips you can give me! If my question needs revising, please let me know so that I can fix it!! I absolutely need some answers here.
The shape of the object.




Cube scaled as appropriate in Edit Mode
Loop Cut to provide vertex density to allow the next step to work.  The edges are shown above.
Curve Modifier.
Smooth Shading
Edge Split Modifier to keep sharp corner where needed and keep smooth shading where needed
I hesitate to comment on material yet I will comment that the dark lines can be achieved with Freestyle which requires more searching and learning.


You can search [Curve Modifier] and [Edge Split].  There will be many matches at BSE.

Hopefully you get more than one answer with different approaches as well.