attempting to make structures spawn on cave floor

Ive been attempting to find methods to spawn structures on the cave floor of a specific biome, using the normal structure spawn parameters did not work for me, instead just spawning in the walls where players would never encounter them.

Ive been attempting to use a placeholder block to mark the location where the structure should spawn, but i can not get it to activate upon generation, it requires player input.

The only way ive found to make the structures correctly spawn has been through using entities to be replaced with the structure upon entity tick update, however this poses the issue of the structures infinitely generating as long as the spawn condition for the entity is met.

Is there something im missing or any possible way i could get this working right?

Any help would be appreciated, but of course is not necessary, if i can find out the solution on my own i will be sure to update this with that information for anyone in the future.