Hey, sounds like you're a solo player. I've been playing on and off, mostly on, since release.

Here's my favourite spots.

1) If you know you're a good shot:

The "Truckstop" with the burning can, 2 bridges after Darthmouth Truckstop. I mean the one where the road splits up to De'Soto's and one down to another gas station. Build right there where the cliff is, you can shoot people coming from both sides, maybe get a free truck. Also, you get 50 Scrap Metal, 10-20 "good" bullets ( sniper / shot ) 10 Metalsheets and 20 Bottles every 15 minutes.

For the "hidden" spots

There is one genius one that's in H10, there is only ONE, literally ONE available space for a groundtamper for extra security if you'd prefer to. Another spot in H1, opposite side of the map, it's literally in the beginning of the woods but in a pit, impossible to see from every angle, and people scouting for bases will miss it because it's completely covered in shadows, and if they patrol, they go "deeper". There's another cliff close to quarantine area in B10 aswell. And my last spot is E1, it's like "4 Stages" of "deeper" into the woods, most people patrolling will go for 1st and 2nd stage, but if they see the 3rd being empty, they won't bother going even deeper. E1 and H10, B10 and H1 had never been raided for me. If you want me to show you the spots, shoot me a private message.