It's a pleasant day outside so I decided to go down to the workshop for a while and press on with the tree trunk.
I made a base for it out of some scrap plywood and this is what I did with that:
Here is the tree trunk sitting on a partial sheet of 1/2" plywood:
I used a compass to draw an outline around the base of the trunk:
The 1/2" thick plywood isn't strong enough on it's own so I used this as a pattern and drew and cut out a second identical piece of plywood and then screwed them together:
I took a disc sander and smoothed off the edges and this is what it looks like right now:
And here it is with the tree trunk on top of it:
You can see in the photo above that the top isn't level and that's the next challenge. Since the trunk is sitting on the base I decided to shove a 2x4 underneath it to see if that would help level things out. You can see that that looks like-not very good:
My husband was helping move the trunk around and he made the comment that placing some wheels directly underneath the trunk and not under base, essentially not using the base at all, might be a better way of leveling the top. I'm going to think about this for the next couple of days and possibly do that instead.