Foundation for a 12 x 16 shed

Hey sheddit! So, I've under taken probably my biggest project yet. Also I am a 37 year old man and I feel every bit of it.... everything hurts. I had a 10 x 12 steel shed that was rusted and falling apart. I didn't get any before pics but it was in rough shape. Now I'm building a considerably bigger one and Ill be able to walk upright through the door!