How to build deck starting in yard, ending on concrete slab

My first thought would be to build the deck in individual 4x8 sections. So you build a frame out of 2x4's or 2x6's with one sheet of plywood on top and the insulation pre-installed between the framing members.

You would then set up your concrete piers and beams that would support the sections. If you use 2x4 framing for the pre-built sections, you would need more beams and piers, but the individual sections would also be lighter and more easily man-portable. Place the pre-built sections on top of the joists and screw them together from underneath.

When you disassemble, you just unscrew the pre-built sections from each other and the joists, take them out in one piece, and stack them on a trailer. Being 4x8, they are the perfect size to fit in just about any trailer or pickup truck and not too heavy for one or two guys to handle. Once those are removed, you can disassemble the beams and piers.

Burying the wood post will cause it to rot prematurely. Even ground-contact rated Pressure Treated lumber won't last forever.

The only benefit of burying the post (besides it being easier to do) is lateral stability. i.e. you can sometimes neglect lateral bracing this way.

Best practice for wood-post decks is to have the concrete extend above grade and use a stand-off post anchor to hold the wood post to concrete.

Here is an example of this with some knee-braces for lateral bracing. The braces don't match so I find this somewhat ugly, but the image is clear and easy to understand.

Footings here don't need to be deep so I often form my own square ones but sometimes I use bigfoot forms and I really like those. Although Shirlock's "mushroom" method is more than adequate if you are only required 8" wide.