You can turn the blocks into vase holders

Maybe you do not want to go all out with the blocks and turn them into a full-blown vase.
You want to turn the blocks into vase holders instead. This idea can give you a bit about what it will look like.
A patch of an amazing proportion

If someone says that you cannot use cinderblocks for anything else aside from building houses or road pavements, show them your lettuce cinderblocks garden, as depicted as below. Invite them over for a lettuce dinner right after.