A simple UV Unwrap?

I have a much divided square and was trying to unwrap it so that it ended up as a rectangle (so a squared texture fits neatly upon it) with the centre vertices along the top and the outside vertices on the bottom, as if one were straightening out a 2D ring.
I thought that you could manage this by pinning the four corners in place and unwrapping it in the default way however the ‘unwrapper’ insists on twisting it in the middle forming some bizarre loop. I was hoping that there might be some small button or method that I’ve overlooked which will stop it trying to retain angles and instead find the simplest, shortest route for the vertices to follow.
Sorry if it’s a stark-staringly obvious answer; no matter how much time I’ve spent tinkering I’m still very much a beginner.(And any ideas would be welcomed gladly. Any way to get round it with mapping to normals perhaps?)

So you are unwrapping a subdivided cube? I would try using the Project From View option, and I think it gives you the ‘bounds’ option with that too, which unwraps it so it to fill the entire space.
(edit) I should elaborate on that a bit…so, you want to select the front and the back faces, from front view, then unwrap them, then go into side view…select only the right and left sides, unwrap them…then go into top view, select the top and bottom faces, and unwrap them. That’s how project from view works. If you loaded it all at once, some faces would just load as little slivers along the edges.