I have made these before - so easy! Lowes sells the 4 to 6" round PVC pipe with holes already drilled. Purchase an end cap, fill with rock, soil, and plant. I will often put these in the center of a very large pot to stabilize, and add amazing height and color to a container that has trailing plants (no end cap or rock needed if you are placing in a container) LOVE THIS!!
For gorgeous containers, use the Thriller/Spiller/Filler method. Choose a taller plant as your thriller, a filler to add around the base and a trailing plant to spill or cascade down the sides. More container garden tips @ themicrogardener.