Step 1: Planing or Fly Cutting Bit
Step 2: Making a Pocket
Set your origin positon as the bottom left corner.
With your rectangle shape selected (highlighted in pink) choose "Create a pocket" from your toolpath options.
Enter your bit information. Assuming you fly cutting bit has a 3" diameter, you can call your bit an end mill with a 3" diameter.
Set your "stepover" at 40%. This is the overlap between passes back and forth and 40% should leave a fairly smooth finish. If you're seeing lines between cuts, you can increase the percentage to make it cleaner. (Keep in mind this also takes longer, so aim for a good balance.)
Set your depth at .0625 or 1/16th inch. We're only skimming not cutting.
Calculate the tool path and save the g-code and you're ready to send it to the machine.