You fit the 36T FRM cog, then the 9-speed 11-34 cassette minus the 11T cog and the lockring, and then a 12T lockring instead..
Would give you a 13-36 would it not, with a stupidly close 34-36 jump from 1st to 2nd gear?
Surely if you wanted to do that properly, you’d use an 11-32 cassette, which would then give you a 12-36 cassette and sensibly spaced jumps the whole way down the cassette.
Though as you can already buy a 12-36 9spd from either SRAM or Shimano, I don’t know why you’d bother!
11-36 9spd would have at least one horribly big ratio jump IMO. Just like on the Alfine hub, where you have the equivalent of an 11-34 cassette but with 8 gears, and there’s a massive gap between 5th and 6th which is really annoying!