Find a lush cave biome
Locate moss blocks naturally generating on the cave floor and around azalea roots
Mine the moss block with any tool or by hand
Use bone meal on a moss block to spread moss and generate more moss blocks
Trade with wandering traders if they offer moss blocks
Find moss blocks in shipwreck or chest loot if available in your version
Use the creative inventory or commands in Creative mode
Use the `/give` command to obtain moss blocks in worlds with cheats enabled