This footing type involves pouring a pad or “cookie” footing at least 12” thick at the bottom of your hole below the frost line. You then set a ground contact rated .60 RET pressure treated wood post on top of the pad and backfill the soil into the hole.  The buried post footing type offers the advantage of reducing the amount of concrete you will need to buy and work with.  It also reclaims almost all of the excavated soil back into the hole, so you will not have to dispose of large amounts of soil as construction waste.  You also do not have to deal with expensive and sometimes confusing concrete anchors and post base hardware.  Embedded posts offer additional lateral (side to side) support to the post that works well to resist wind loads. 

Some deck builders reject this technique because they do not feel comfortable putting a wood post in the ground under any circumstances for fear that it will rot.  If you do decide on using a buried post footing style you must be sure to use a .60 RET treated post that is rated to be buried in the ground.  This post will contain a higher concentration of treatment chemicals than standard treated wood that will protect it from decay while buried.  This is the same type of wood that is used for other kinds of foundations.  The pressure treatment companies insist that these posts will last longer in the ground than the deck frame that is built above it. The only obvious disadvantage is that if the post is ever damaged, it will be very difficult to replace.  Some deck builders like to surround the post with gravel to promote drainage away from the wood post and footing.  Because the footing is buried, you will not need to be quite as precise to set the post on the exact center of the footing with your post as you would with an exposed footing.