Teaching puppy to be home alone

So my puppy just turned 6 months and since I got home I have been working from home and its been nice spending so much time with him and training him. I just got notice that in January i will need to move from fully remote to hybrid (so like 3 days in the office). My pup has been ok when by himself so far. He is fine being in another room or in the backyard without me, and when i leave the house he is ok mostly. I have noticed that if im gone for longer however he does get a bit upset like lots of whining. I will be gone for about 6 hours when i go to work in the office, if you guys could drop advice on how you prepared your pup to be home alone that would be great. I would really like to get to the point where he can just free roam in the house and not in the crate the whole time so any advice would be greatly appreciated!