I have a video to prove just how easy Day 7 was with a basic horde night base.
Obviously later hordes would require more than this but it is intended to be modular so expandable easily and upgradeable etc.
Molotov's and clumping are the key, plus enough spikes.
Disclaimer: sorry bad english, isn't my first language.
My first horde night (solo, normal difficulty, 16 zombies) was the same: initial pressure and then by midnight it was over. I'm not a good player, but what I learned in A16 still helpful: built a two floor cage 5x5 with 10 rows of wood spikes and an extra row of barbed wire fence (which was useless because they jump it). Patch notes gave me an idea because horde will always come from easiest path, so (I'm playing Navezgane) I built the horde defence between a hill, which by any means is hard to go through, but not a clear path, and a bookstore (my bedroll is on top of it to avoid spawn inside the building). So in theory, they "only" had 2 clear paths in order to reach my cage. They still reached my walls, but it's sealed so zombies first ran around of it and then start to attack. No "zombie luck": spikes are super weak, but with ten rolls it killed a good amount of zombies and I think very few got my walls (I'm not sure exact numbers, but no more than 12 zombies) and not attacking the same spot was easy to kill with headshots. I'm about to take on the second horde in the same base, but now I have 8 rows of iron spikes, 2 rows of wood spikes and 1 row of barbed wire fence. I don't think it will be enough because it seems gamestage is scaling too fast from what I've seen so far.
Overall, I think game needs a little bit balance specially for solo players. I disagree to Roland: I should not need to tone down settings just because I'm solo. If that's the case it's pretty clear game needs adjustment. From a builder first solo player persperctive:
1) Gamestage should be a little less harsh for solo players
2) Bonus when attacking blocks should be toned down (except digging, it's perfect because hidding underground is BS, imo)
3) More hit points for spikes and a steel spike type because it would give us a much stronger passive defense, but not at a point I can relax, drink my coffee and watch tv until horde night is over
4) We still need a better way to get more bones (adding gore blocks to roads is a good idea, but nowhere near enough), otherwise crafting paper (looting is not doable since 30 days respawn is good enough), duct tape and glue (there are tons of recipes which requires both and looting a fairly amount weekly isn't possible) aren't an option anymore. For example: to take on late big hordes on A16 I always needed 100 ~ 150 exploding bolts and 2 ~ 2.5K shotgun shells; in A17 it's virtually impossible to craft that in a 7 days span
5) For the love of Gods: do not touch POI's (except those annoying weird spawns right behind you)