Insulating method? Shed floor.

Someone is going to give me a fairly lightly built wood frame 12 by 20 shed; which I will have to take apart in order to move from rear of their city lot. Hoping to salvage as much as possible of its material using own labour and taking time.
Intend to rebuild as a 14 by 24 using additional materials etc. on posts/ concrete pipe set into concrete, below ground having used this method several times previously for several sheds and a cabin.
Here it is necessary to go at least 30 inches deep for frost; even if one places insulation at or just below ground level around each post .
Would like to insulate and vapour barrier the floor while building the new shed, with a view to perhaps later insulating the walls and ceiling.
Question: What would be the best method of either supporting say, foam cut to fit between the floor joists and/or laying insulation some kind of mesh stapled to bottom of joists, or thin plywood ether nailed (glued?) up to bottom of joists or laid into joist spaces on some kind supports. It one of those things that if you don't do it while building it will be difficult/impossible to do later?
If possible will use closed cell foam in the floor, rather than styro or glass wool/loose insulation to avoid water/damp retention. Not more than 8 to 15 inches below bottom edge of floor joists; slightly sloping ground!
Would very much welcome ideas/advice. Far 'out of the box' suggestions OK.
Terry
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Wood will rot or possibly be attacked by insects. Either use pressure treated wood or metal straps as step 2. Step one is to cut the foam for a pressure fit and put some urethane adhisive on it and press to the bottom of the floor. As for doing it later, you'd have a heck of a time with 8" of clearance.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.