Minecraft wiki entry for Configured_feature, associated text: fossil—Can place a small structure.
 fossil_structures:
: A fossil structure.
 overlay_structures:
: An overlay structure.
 fossil_processors
Template:Nbt inherit/structure processor
 overlay_processors
Template:Nbt inherit/structure processor
 max_empty_corners_allowed: How many corners of the structure are allowed to be empty for it to generate. Prevents structures floating in the air.