More specifically, can a Snorlax be bred to know softboiled?
Nope, only the Chansey, Clefairy and Togepi lines can learn Softboiled. (Also Mew could learn the TM in the first generation and via move tutor in gen 3.)
Snorlax learns Rest though, and has high HP which works out pretty well for it.
ONLY pkmn able to know softboiled are chansey and blissey