Open a crafting table interface (if you want to craft it)
Get bone blocks by crafting: place 3×3 bones (Bone item) in the crafting grid to create a Bone Block
Alternatively, find Bone Blocks in Minecraft Creative mode inventory (search “Bone Block”)
In Survival, mine Bone Blocks only if you already have them (they cannot be obtained directly from mobs/structures as a block in most versions)