CNC routers can be leveled differently than one would normally level their 3D printer bed. Instead of adjusting the height of 3 or 4 points on the cutting platform to match the router path, an opposite approach can be used. By cutting away at a sacrificial piece of material mounted to the bed of the Mill One, the bed will now be 'level' relative to the routers path.
Download the g-code file and run it so that your machine will automatically perform this operation. Once your sacrificial board is ready, you'll be ready to start cutting on your Mill One!
See more about this process here: https://sienci.com/mill-one-v2-manual/preparing-to-cut/