Scrounge some wood pallets that are in good condition and, if they are wider than about 24", cut them in half. Assuming that there are three runners, cut just to the side of the center one and save the pallet half with two runners. Disassemble the other half and use it for firewood OR add another runner (usually a 2x4 will work) and build yourself another narrow pallet.
Make sure you can get a 2x4 in between the end topboard and the board next to it.
Measure the distance between the basement floor and the top of the floor joists. Measure the height of the pallet. If the floor to joist top is 90" and the pallet is 5", subtract 5 from 90 to get the maximum 2x4 length of 85". Better still, make it 1" shorter to make assembly easier. BEFORE YOU CUT: make sure the 2x4 cut to 84" will safely sit on the floor and lean against the floor joist.