The only way we've found of getting DS3 to settle on his own is by putting him down slightly on his side, if we put him on his back he either a) wakes up straight away or b) only sleeps for about 5 minutes. On his side he sleeps really quite well (for a newborn ).
I know the advice is flat on back because of the risk of SIDS but is it really terrible of us to prop him on his side??