Thanks for the ideas.

The table has a arch in both directions (length and width). So, every slat would be different (I'm more of a software/electronics guy than a steel guy). I've had lots of ideas but nothing that I figured would work.

I thought that using a 3 small pieces of angle running length wise (each side and middle) I would easily get a good level. I just don't think that I can use heavy enough angle so that it wouldn't bow but still bit in the water pan.

I'm afraid that if I try cutting custom templates for each slat I won't be able to get it precise enough to be worth the effort.

Short term, I think the shim method is probably the best bet. That seems like it would get me to test cuts the fastest (doesn't everybody want instant gratification?).

Once I can use the table to cut, would the following work?
1. Run a string along each side so that I can mark level at the end of each slat.
2. Use the table to cut each slat from one mark to the other.