Recorded in 2006 Bob Dylan’s Modern Times is well executed and mostly relaxed, if you can take bobs gravel vocals.
Keb’ Mo has a ton of nice and easy bluesy stuff, also very well put together and supremely recorded.
For me it would be the Sensational Nightingales, but that doesn't seem to be what you're looking for, nor does John Scofield's "A Moment's Peace", though you might try it. Norah Jones' stuff is generally pretty mellow (her live album is a little more hard hitting), though there's plenty there worth paying attention to. More toward the jazz side, Shirley Horne does mellow very well; if I had to recommend one, "Light out of Darkness", a Ray Charles tribute, might be to your taste. J.J. Cale's the man for laid back rock and roll. John Prine could be your guy, but I can't recommend a specific album. Emmy Lou Harris's gospel album "Angel Band" could fit the bill.