I made this for Dad for Father's Day and it was simple and easy! I am making a few for my house too.
All you need is 2 plastic salad bowls. One large family size and one medium size, so they fit, one inside the other. Spray the inside of your large bowl with regular cooking spray the outside of your smaller bowl. Set aside.
Mix your concrete according to package directions - I used Quickcrete ready to use concrete, the smallest bag they had, a 10 lb bag. One bag made one container.
Pour concrete batter into the large salad bowl and then nestle in smaller bowl. Push small bowl into concrete so concrete oozes all around sides of bowl. Weigh it down with a brick or other heavy object. Add rocks or seashells around edges that are showing. Let dry and twist it out (It should not stick at all with the cooking spray you used). I think mine took 2 days to completely dry but with all the rain we were having I am not surprised.
I added some dirt and small pepper plants but it would also look cute with seashells on your edges, filled with sand and a candle. Super easy.