Due to the slope in my backyard, I also purchased six 8"x48" sono tubes (seen above). Sono tubes are typically used as a cylindrical footing for decks or perhaps even small barns. Dig a hole slightly larger than the sono tube with a post-hole digger to the depth required (for me, roughly 4' to 1.5' depending on location), insert the sono tube, place a couple inches of stone for drainage at the bottom, then concrete. For my application, I wanted some additional support due to the slope of the yard. Overkill, perhaps, better safe than sorry, right?
The following week was very humid and muggy... PERFECT weather for the concrete to slowly cure to full strength. Typically, you can wait 24 hours to remove the formwork, however, with the amount of moisture in the air, the concrete was too "green". The form needed to stay in place until the concrete reached that pale gray color. Besides, I had plenty of time before the flock moved in, so I waited until the following weekend to strip the forms.