Oh, I'm the worst person to ask on puppies - I usually get them when they're over a year. All my dogs have been rescues for years! Plus they've all always slept with me, lol.
But I do remember my parents putting a hot water bottle and a clock with a "clicker" in our sheltie's bed when we got him as a puppy. It's supposed to make them feel they are still next to their mother.
(And no, I promise not to get on my soapbox about 1/2 breed dogs being sold as "designer" dogs
)