Build a border around an existing planting bed or choose a site for a new raised planter. If you're building a new planter, find a site that offers full, bright sunshine and mark off your desired square footage.
Use a shovel to dig a 3-inch-deep ditch around the borders of your planned bed. This ditch should be just wide enough to accommodate your concrete blocks and long enough to fit the blocks end-to-end along the border of the planter. Lay the blocks in the ditch to build a foundation for your planter wall. This will keep the wall from slipping one way or another.
Stack another layer of concrete blocks on top of the first and continue to add layers until your wall reaches your desired height. This wall does not have to support heavy weight, so it does not require cement.