The concrete piers for the northwest (final) container are really high. I use a solid concrete block for the base, a hollow block in the middle and another solid block on top to support the container. The blocks are glued together with Gorilla Ultimate Adhesive, which is actually better than conventional mortar.
I poured two concrete blocks to mount the entry gate. I was surprised that each block took about 40 lbs of concrete. The gate is screwed to the concrete pads with Tapcon anchors.