I bought several bags of vermiculite from Menards to use as insulation in the concrete block. It wasn’t that expensive, and it should help a little to keep the cold out. I did a little research and I could have used spray foam or used foam insulation on the bottom. Both of which would have been more expensive and I don’t think would have made much of a difference.
Built this “trolly” out of some scrap. I poured the vermiculite in the top and just slid it across the block, lifting it where the anchor bolts were set.