Cutting on the bottom side?

[eradicatore]

I want to make a trivet for valentine's day. I'm close, but I'm not sure how to "cut from the bottom". Right now I have this:

How can I cut the cross pattern on the bottom side of that board? Or do I have to just drill two alignment pin holes, and flip it over? I.e. I can't use vcarve to show a demo of this... I guess that's fine.

Like this guy did: https://youtu.be/RHGG7lLQipA?t=70

Here is the vector view:

[eradicatore]

Should I ask this in another room maybe? Sorry if I picked the wrong place. Seemed ok as a question about how to use UCCNC on the bottom of a board.

[cncdrive]

Yes, usually how it is done is with some positioning pins on the board.
Then you can flip the board over and the pins will keep the 2 sides in syncron.