This is a frequently broached subject around here, and I just finished cutting down about 30 cords of split wood from 22” to 18”, myself. I settled on what I think is the best way to do the job, but others may have their own ways, which suit their equipment and work methods.
I built a rack that’s about 6 feet tall, 18 inches deep, and as wide as the longest bar I like to normally run (28 inches, in my case). The rack is all open framing, with the only sheathed surface being the solid plywood back, which controls that 18 inch dimension to which I’m trying to cut. I stack about 0.4 face cord in that rack, run a ratchet strap around the whole thing, and then with one pass of the saw take it all down from 22 to 18 inches. The rack is built with no nails in the areas where the saw will inevitably chew on it, using glued dowels there, to avoid chain damage or injury. Each rack build takes me under an hour, and is good for 15 - 20 cords, before it’s pretty much shot.
It is shown/described a little in this thread I’m linking below. I would just cut down the wood one cord at a time, as I was ready to haul it up to the house to burn. In that way, cutting down 30 cords took me just a hair over 3 years.
https://www.hearth.com/talk/threads/homemade-or-diy-wood-tools-equipment.169151/#post-2271432