Working through the chess section now, and Mike set his origin by selecting the face/ attaching the cursor/ setting origin to cursor. I set mine by placing the model at 0x0x0, and setting cursor at 0x0x(Dimension Y/2).
Also set model at 0x0x0 by dividing dimension Y by 2.
Math is reeeeally not my jam… does my math check out?
Um, maths tends not to come into it. Certainly not for me. 
You can select the bottom face and move the 3d cursor to it.
Then the origin point to the 3D cursor.
Then the object will centre on the Origin point as usual, but by placing it on the base you are able to keep it at the board level.
Yes, I don’t use math for this either. I just zoom in close, and raise the object carefully so it’s on the floor (board of a chess set), and then reset the origin point to 3D Cursor.
Its part of why I am trepidatious about this obsession with geometry nodes currently, modelling by maths is not my way.
To tell the truth, when I finally downloaded and installed Blender 2.93, I spent a lot of time (and still am) just trying to find everything in the UI, and when I saw Geometry Nodes, I sat here scratching my head trying to figure out what on Earth they could be, and what they would be used for.
I doubt I’ll be playing with them any time soon.
oh yeah, my math equations within blender will certainly never be more complicated than very basic math problems 
but it IS nice to know that it does the work for you… all you have to do is type the equation into the desired field.
Difficult to get a grasp of your method, because w need more info.
The 3D cursor is just a tool to have a fixed point in space beside the world one 0,0,0.
If you do math in object mode, you are basically working with the origin point. The virtual center of the object. But it can have any location you need or want it.
In edit mode, you manipulate the mesh of the object, but the origin stays unchanged. Moving the mesh is basically moving the object. Because the origin point stays at the same WORLD location. But the object’s content (the mesh) has transformed.
While moving the origin point in OBJECT MODE, the mesh stays in place.
The reason for us being confused is that “y / 2” does something half, but half of what?
If the origin point is in the middle of Y, then yes “y/2” could work. But we don’t know your object (mesh and location or the origin point).
Remember there are many possible solutions for Blender situations. There is no real right or wrong. The end results count. It’s more or less how efficient it can be done. And that takes practice and experience.
and that would be one reason why i suck at math… i’m always leaving out vital information! yes, i was talking about dividing the given origin point (the center of the object) in half to drop the origin point to the bottom of the object. that number is where i would place the cursor to then “set origin to cursor”.
also, nope. this is a long way to nowhere. ended up having to drop my model to 0x0x0, setting cursor to bottom, and setting origin to cursor per method shown in video
ah, well.
If your origin point in your objects mesh is correct. But this origin point is not at location 0,0,0 anymore.
Then press shift c to set the 3D cursor (reset viewport) on location 0,0,0
Then you can give the command to move the object to the 3D cursor.
Resulting in the origin point of your object being at the location of the 3D cursor which is at 0,0,0
If you are bad at math or confused by the dimension of your object.
Then in edit mode select the bottom face. Then give the command cursor to selected (Shift s).
Exit edit mode and in object mode origin to 3D cursor.
A lot of manipulations. But it is part of 3D design and you will be using this frequently if projects are growing in complexity