The way I do it is dial in your altitude then hit TO, when you’re ready to turn on AP it comes on as Roll/Pitch.
Pitch doesn’t work well for me so I normally go Hdg/VS clean up and let the aircraft accelerate to 240kts and then hit FLC.
If I’m changing altitude (climbing) then dial in new altitude hit FLC and increase thrust to climb, if I’m much faster than 250 then I’ll drop the speed bug down to 240/250…
Works for me anyway…