Here I will show you how to build a cheap shipping container or sea van foundation. We used 55 gallon drums to hold the concrete instead of sonotubes. You can find these drums cheap or even free if you look for them. You could probably set the containers on a gravel pad but these piers are set to perfect height with a laser level and it will keep everything level for the build. Well worth the effort after all this will have a 40 foot roof system on it and hold a snow load.