Splitting block?

I use An unsplit round as a base

Yep unsplit round. Some folks use tires, ratchet straps, bungees to keep splits in one place.

Yeah, the ground absorbs your blow and steals some of your power. A heavy cut with a big diameter works nicely

I do it mostly on the ground. Yup it's soft, but the time and energy to pick up logs and put them on something is too much IMO. And with a not great back, bending over to pick up anything is no fun.

If i do want to split a log on something i roll it onto a short knotty round. Maybe around 6"-9" in height.

I just do it on the ground when I split with a maul. I kinda move to where the logs are rather than bringing each log to me. That way I’m not creating the depression in the ground or moving whole logs around. If your splitting kindling, then yes, a nice chopping block is handy.

This is the only way at my age that I'll do any splitting

I've got a big oak round I cut years ago which I cut mostly flat across, but about 1/3 of the diameter is cut at a slight downward slope. That way, if I'm splitting rounds that were cut squarely, I set them on the flat part. If the round I'm going to split wasn't cut squarely, I set it on the slanted part and rotate it until it stands up straight. Of course in a perfect world I would cut them all squarely, but I haven't ascended to that level of chainsaw-wielding yet.

Also seconding the folks that suggested using a gnarly piece. The knottier the better for your splitting stump.... I used a big oak crotch at one time too which also held up well.

I put a tire on top of my splitting log. It works OK. If I am splitting one round in the tire it is semi helpful. Half the time the splits hit the ground anyway. I find it much more helpful if I am positioning 2 or more logs for splitting. If I fill the inside of the tire somewhat with logs, I can stand up some that are cut a little crooked, they kind of hold each other up while I split them, and a good percentage of the splits stay in the tire.

Many of the logs I get are too big to fit in the tire, so I have to pre split before they go into it.

I don't love is that it fills up with shrapnel and bark. You can't just wipe it off. If I don't clean it out, it will trun to bark mud after a rain.

Before I got the splitter, I used an un-split round. Only do that now when checking a random split for MC

My answer might not help much but i use to have a hydrauluc splitter that was a b**** to start pardon my french so i switched to an 8lb maul and wedges and pretty much been goin at things that way for about 8 yrs i never really got into splitting stuff on a block b/c it kinda felt odd to me but i also occasionally wrap a chain around logs to keep everything right there

I buried a 20" dia. hedge round leaving about 2" above ground which allows me to mow over it. Don't have to lift rounds and very solid. Will outlast me.

I tried replacing the rounds I would split on. I built a steel base base and put a rubber top. Never got the rubber right. It was to soft.
If your in for the long term, get a splitter.