Open Minecraft
Find a river, lake, beach, or shallow water area
Look for clay blocks underwater or along the shore
Use a shovel or any tool to mine the clay blocks
Collect the clay balls that drop
Smelt clay balls in a furnace to make clay blocks
Place clay blocks where you want them in your build
Break clay blocks with a shovel to get clay balls again
Use a crafting table to turn clay balls into bricks if needed