Starting with the floor bed in the room you typically cosleep in is a super helpful way to go about starting! Having it in the same room & placing them there for naps before you expect them to sleep over night there is definitely something that helped out big time
I don’t know if this would benefit you age child cause my son is 3 now but what we did was stay in bed until they were asleep then get out of the bed and just keep doing that until they get the hang of it. Being that my son is 3 now were in the process of getting him to go to sleep on his own.