What kind of flooring for crawl space that is easy to move on?
For temporary storage of items on a concrete floor in a crawl space, I'd suggest some cedar planks. After building our fence with cedar pickets, we have stacks of 18-24&quot; cedar pickets, and use them any time we need to store items, particularly items that may be susceptible to water damage, on our garage floor.
A single 6' picket could be cut into 3 24&quot; lengths. The lengths could be used individually for smaller items, or they could be ganged together to make a wider platform. IIRC, the pickets were 5-1/2&quot; wide, so two widths would be 11&quot;, three would be 16-1/2&quot; wide.
Use a piece of cheap 1x2 at each end to hold the pickets together into a &quot;pallet&quot;. This will keep the pieces together and make a handle that will keep the boxes on from being pushed off, as well as being a good handle to pull with.

They're thin at only about 1/2&quot;, so they won't take up much of your limited height.
They're naturally rot resistant, so if water seeps through the concrete or you get some minor flooding, they'll still last a long time, and they'll protect the cardboard boxen on top.
They are a bit grippy and may not slide quite as easily as desired, but, with the handle they should push or pull reasonably well.