Structures in 1.18.2 - how to make underground part?!

[Mad Alchemist]

I have ported most of my mod from 1.16.5 to 1.18.2, but stuck with porting structures... In 1.16.5, there was java code where it was possible to adjust structure height.
Code was entirely based on TelepathicGrunt's tutorials. I didn't succeeded in porting 1.16.5 code to 1.18.2, and then found the same tutorial updated to 1.18.2, but... There was no java code anymore! Structures in 1.18.2 can be generated using .nbt and JSON only. Ok, it's even easier, I thought then. But... Whenever I use structure block to save my structure to .nbt file and then using this .nbt to spawn my structure, every part is generated above ground. I am trying to make a well with drowned spawner inside, but it always spawns as a weird tower filled with water. No matter where I put my structure block - below structure, on top of it, or at ground level (in creative world where I build it, structure itself is placed as if it was generated as intended) - it always spawns with it's bottom on surface.
How do I adjust structure placement in 1.18.2?