putting one of these adapters in. So removed the center filter mount "bolt" and this tin plate fell off with a gasket behind it to the engine (call this gasket 1).
So I have a gasket kit which is a big flat gasket like the gasket on the engine which I call "new gasket". a thick cork o ring and thinner o ring. along with the long bolt and the 90 degree aluminum piece.

What is the proper order to put things back on?

Most importantly,
Do I need to reuse the flat tin plate (with its existing gasket)?

My first thought is,

1.leave orig gasket there,

2.pop the tin plate back on,
next is the new large flat gasket same size as one stuck to block

3. put alum adapter on

4. put the two smaller gaskets on bolt, then tighten up.

I'm thinking that may not be right and appreciate any comments please.

remove the flat plate/gasket & clean the block circular recess squeaky clean. the thin washer goes on the bolt before you insert it into the adapter then the thick washer goes on the bolt after it is inserted into the adapter. Use some cement on the circular gasket & have the adapter "clocked" correct like you want it as you raise it up into position so you don't have to "rotate" it once it is in place in the circular recess. cement the gasket up on the block first & confirm it stays in place as you raise the adapter in position & that it (gasket/adapter) are now seated correctly all the way in place then tighten the bolt (50 lbs iirc but I would check). On a hi perf app I would port the adapter innards as it does have some restricted right angle turns. EDIT & add more holes in the bolt.

To install a factory 90 degree adapter. The oil filter base plate is not used.
1. large round gasket glued to the block.
2. small thinner gasket under the bolt head
3. insert bolt into adapter
4. thicker small (cork?) gasket on bolt
5. install adapter to the angle you prefer and tighten.
Note: One time many years ago I could not get my adapter tight enough. I found the large bolt was too long and it was bottoming out. I ground it down some. Yours is probably fine but i just wanted you to be aware if you have that issue I had. Maybe it was a mismatch of parts

Thanks RapidRobert. Will drill a couple extra holes in the bolt.
Cheers!

Thanks mopars4ever. Thanks for the reply and the tip!