I think a land-based coral-like creature (might also be a plant) would work well as an symbiotic insect hive.
Similarly to corals this (stationary) creature lives of organic matter, which it gathers from its surroundings: using a paralyzing venom against (small) creatures that come near it, it can obtain food. It might also be able to digest other plants, using vines similar to poison ivy, and of course being poisonous is also a good way to prevent being eaten by bigger animals.
The insects using this creature as a hive are of course immune to the paralysing venome (as clownfish are immune to sea annemones), which allows them to hide and nest within the plant.
This tendency to nest in the plant over time evolved into a full blown symbiotic relationship:
* the insects gather food (like bees) and store it in their hive, if the plant doesn't get other food it can also live of these reserves
* The insects can drag dead animals (like mice or small birds) or other large food itens they find to the hive. This secures the food from any other competitors that like to feed on them (once in/on the hive only the insects and the hive can feed on it).
* Additionally and predators chasing the insects can be lured to hive and thereby become food themselves (since the hive will paralyze and slowly kill them, also the insects can now grab a bite from the former predator).
This might even evolve so far that the hive recognises not the insects but specifically the (female/worker) descendants of a particular insect queen (by DNA/pheromones) and doesn't even allow any other swarms of the same species in.
* In case of short last bad weather or other conditions the insects can live of the reserves the accumulated, or also on not fully digested prey of the hive.
* The hive gives the insects almost impenetrable protection: smaller animals, other insects and so on are food for the hive and most bigger animals ignore the hive and anything in it since its poisonous. This allows the insects to also leaves food storages and eggs or not fully developed newborns without in the hive without having to worry about predators.
* The size of the hive creature can range from very small to huge - mostly depending on how much (extra) food the insects can gather. 445
If they are able to gather extra food the hive will thrive and in turn the swarm can grow. If may insects die or the hive gets damaged than the other partner starts dying of until they both match capacity again and can regrow together.
* In case of long (several months) winters both the insects and the hive probably won't see a lot of food for a long time. In this case the queen and small part of the insects can retreat into the core of the hive and life of reserves. Any other insects that can't get enough food, can serve as nutrients for the hive (the hive only consumes dead animals, the insects are the only ones normally surviving contact); but the hive will likely also loose biomass and wither until only the core with the incest queen & associates remains.
* Without insects the hive can only grow passively and very slowly. However every time a new queen is born (or an insect swarm needs to relocated) the queen takes a part of the plant with it to grow a new hive from the seedling.
* Further symbiotic evolution might lead to a heat regulated central chamber / core for the hive queen (or eggs)
While you said you'll ignore evolution of the hive / symbiosis for now, I think it's pretty clear how it might have worked here:
* the insects somehow developed immunity to the hive paralysis venom and started nesting there
* the insects figure out that any food stored / dragged to the hive is protected from all other creatures that would compete over it
* from this point onwards the hive gains a huge benefit from the insects nesting in it, leading to symbiotic evolution 445