I hate to say this, but it seems like a pretty clear case of using the wrong tool for the job.
There's no conceivable reason to cut something this simple on a large-format CNC mill. It's literally just a couple of straight cuts. It's not going to be faster (not with standard endmills), not going to be easier, and it's not going to be cheaper unless you're making them by the thousands.
You can likely buy S4S lumber for less than an oversized sheet of furniture-grade 1" plywood.
There's no conceivable reason to cut something this simple on a large-format CNC mill. It's literally just a couple of straight cuts. It's not going to be faster (not with standard endmills), not going to be easier, and it's not going to be cheaper unless you're making them by the thousands.
You can likely buy S4S lumber for less than an oversized sheet of furniture-grade 1" plywood.