(I'm going back a few steps to make the idea better. This is a simulation of what would happen, not the actual process.)
http://scp-wiki.wikidot.com/ideation
Step 1: choosing two random words.
Sandcastle.
Civilization.
Step 2: combining those words.
Sandcastle civilization.
Step 3: making the "concrete idea".
A civilization that inhabits a Sandcastle.
Cool another way the "concrete idea" could have been:
A civilization made of sentient Sandcastles.
Step 4.1: expand the abstract (identify the objective).
Making the reader feel: helpless (but not too much).
Because:
If a small wave comes, people can hide inside castles and resist it. Castles are strong.
Sandcastles (usually) cannot resist a small wave. They just don't have a good foundation, they are weak.
People enjoy being protected. People dislike being unable to protect themselves.
Step 4.2: expand the abstract (how to reach the objectives).
Fear of: vulnerability.
How to play off this: The civilization must feel protected at first. Perhaps the damage to the castle has been slow or hard to notice. The civilization could felt too confident, but this wave was too big.
Secondary fear of: sudden death.
How to play off this: Waves are unpredictable. Picture the following: the civilization was caught off-guard. The Foundation acted too late, and the wave took over everything without previous warning.
Establish a link between the reader and the civilization. Make the reader relate to it and feel safe too, then "attack". Also, don't completely destroy the anomaly. That would be bad.
Step 5: expand the physical.
What does a Sandcastle has to do with a Civilization?
There were many civilizations that built castles in the world. The most famous of which was the medieval civilizations, which built castles to protect the people.
Castle-like things were built for the same reason: forts, fortified houses, and big walls. Also, "to fortify" means "to provide (a place) with defensive works as a protection against attack."
Sandcastles are just miniature versions of normal castles, so the symbolism makes sense.
What if we had a civilization that was a tiny version of medieval civilizations? It could build small-scale castles made of sand, make mini forts, live in petite houses, or even make miniature walls.
Why does the Foundation hide the existence of this civilization from the world?
The civilization is a small, controlled group that can be observed to see accurate situations of what really happened in the Middle Ages day-to-day lives, but it is being kept a secret.
Why are real-world science tools kept restricted?
Sometimes they are rare, almost unique.
Maybe this is one of the only civilizations of this kind left. This could be the answer, but:
Why are these civilizations so rare?
Sometimes, they are very fragile.
Could it be that they themselves are made of a sand-clay substance, hard enough to sustain itself but hardens quickly in water and becomes a statue? That would explain most things (as sandcastles are mostly built on the beach, therefore close to water), but there should be more to it.
Sometimes, they are self-destructive.
History shows that civilizations are likely to engage in wars when there are other civilizations nearby. This also explains why the small amount of castles (and make a cool narrative), but the answer still doesn't feel complete.
Sometimes, they are recent.
Here is the final piece of the puzzle: no one said these kingdoms were ancient, hundred years-old living sculptures. Anomalies are made and neutralized, nothing blocks the castles from being built yesterday.
So, how many castles are there?
Currently three, all on the same isolated beach. Two of them are fighting while a third, farther one, is reinforcing its defenses. During an intense fight between the first two, a wave comes and wipes out the population of both, while the third one was able to survive due to preparation. The Foundation would then protect the third kingdom from the water and that's it.
But it being recent creates a huge problem: who or what built it?
What is the backstory?
The backstory:
The area anomalously took the form of miniature castles with tiny houses and mini living people. A few days later, The Foundation noticed the anomalous activity and decided to investigate. The rest of the backstory is irrelevant to understand the article but has to do with something that happened there months prior.
What happened?
Again, irrelevant. I plan on going deeper into this backstory in another article, with a cross-link or something.
What is the central narrative?
A great narrative is the source of a great article.
The narrative:
The Foundation would send waves of miniature exploration drones (controlled by an exploration team) inside those houses and castles, making a total of three exploration logs (one for each castle). Then, they would see how the castles interact with each other ("testing").
A few narrative details - to connect the reader to the citizens and the castles - later, two of the castles would engage in war. The whole thing would be shown as an incident report with a video log attached to it, then be brutally interrupted by an innocent wave. This wave would annihilate both armies, leaving solid carcasses on the way back. The two castle's walls would be destroyed and there'd be no survivors in both.
The third castle, however, would survive the water (a glimpse of hope I plan on not tearing apart) and receive extra attention from the Foundation. The bodies of the armies would be studied to see how do they work, while the castle left would obtain toggleable walls and ceilings far enough from it to not intervene but close enough to protect from waves and rain.
The end.
More questions to come
Per 
