1. I bought from a fantech.net distributor all the inline blowing guts needed to pull kitchen exhaust.
2. I went to a metal shop and had galvanized metal folded, to fit inside a stud wall cavity, turn 90 degrees and change shape ("adapt") to meet a round duct.
That was in 2009.
My cost up to that point was a few hundred all told, for both air extraction mechanics and custom made ducting in the wall.
I guess that means I had my "Liner" custom made. Or "liner insert".

A separate item from the above is the canopy (capture volume) over the cooktop, for which I'll use stainless steel and tempered glass.
My shape will be different from yours.
Mine is to fit under wall cabinets.

arbordomus posted something he made in his thread in 2009.
He also bought the parts and put his own solution together.

From Fantech I also bought the damper to prevent backdraft.
There may be hundreds of things for you to learn, or maybe not.
A lot depends on who you know who can guide you, when you want to double check things.
Internet-gleaned knowledge is OK up to a point.

I rejected the idea of buying an "insert" for three reasons.
I wanted a fan to be blowing far away from my ears;
that is why I went with an inline fan.
(AND it was worth it!!)
I wanted to have more space available for my wall cabinets and backlit shelves;
that is why I had to dump the idea of having a fan housed in a box right where I wanted to have continuous shelves and uppers.
(Of course I'm happy about this too.)
I wanted to benefit from separating out the various costs and putting the package together all by myself:
that is why I rejected the idea of buying a whole kit from a "broan" type manufacturer.
I called them a lot and got a feel...
These firms need to justify lots of salaries and corporate margins.
Exhaust fan parts are available (with profit embedded in the price) from the suppliers.
Ducting was easy.
Shaping a beautiful smoke capture device is not rocket science either.
I'm taking my time with this last step, because I have the time. : - )

HTH

Thanks davidro, it does help. There are more ways to do this than I had been contemplating.