The Solo Wipe That Survives Past Day Two
Solo players lose bases to attention, not to firepower. Being unremarkable is a defensive stat, and you can build for it.
A solo base does not have to be unraidable. It has to be not worth raiding, and then not worth returning to.
Start with placement. A base on a main road with a visible tower advertises that someone is home and that there is loot to take. A base slightly off the road, without a silhouette on the skyline, behind terrain that hides its footprint, gets walked past. The cheapest wall you will ever build is not being looked at.
Then build for cost per wall rather than size. A small base with genuine honeycomb around the loot room costs a raider more explosives than a large base with thin walls and a hollow interior, and it costs you less upkeep to hold. Do not leave an external door where a raider can start work out of sight; do not put your loot room against an outside wall.
Spread the loss. Two stashes away from the base, holding your spare gun and enough resources to rebuild, mean a successful raid on you takes your kit but not your wipe. Keep the good stuff you are not using out of the base entirely. This one habit is the difference between being raided and being finished.
Last, plan your own exit. Know two ways out of your own base that do not walk you into the raid, and keep them clear. Most solos die inside their own front door, defending a room they had already lost, with a full inventory they could have carried out.