See these four Maro articles for details

Intentional Design Skeleton

No Slot:
Homestead Guardian (creature, medium, vigilance, landfall)
Deadfall (instant)
Sludgeblast (instant)
Cobbled Realm (sorcery)
Beneficent Druid (creature, small, landfall)
Crucible Forge (land)
Volcanic Activity (enchantment)

Generated Design Skeleton

CW01 — creature, medium, vigilance, landfall
CB01 — instant
CB02 — instant
CG01 — sorcery
UG02 — creature, small, landfall
UC01 — land
RR01 — enchantment