Stand a paver up on one of its narrow edges on a flat, clean work surface. Draw a wavy line of construction adhesive over the left long edge of the paver.
Stand a second paver up on one narrow edge and press one of its long sides at a right angle into the construction adhesive on the first paver, making the corner edges flush. Draw a wavy line of construction adhesive on the left edge of the second paver and add a third paver the same way. The fourth paver should be glued to both the third and first pavers.
Allow the construction adhesive to dry for about 24 hours. You should have a rectangular tube at this point.
Draw a bead of construction adhesive over the top edges of your rectangular tube. Place a final paver like a lid on the adhesive. Let the lid dry for about 24 hours as well.
Flip the planter over so the open side is up. Use your new planter in a level place away from excessive moisture.