I have a cinder block wall that is falling apart. I will replace it with a cedar fence. I'd like to re-use the cinder block to create an 18" seat wall/planter around the perimeter of my property. Does anyone know where I can get step-by-step instructions on how to do this? Do I need to use mortar or rebar? Do I need to allow for drainage if I am going to use it as a planter?