You can use the round board template to create your circular board outline. From the File menu select open template and select the round board. To get the appropriate size you should start by setting your grid, by pressing the g key, and setting it to the radius of your circle. Next left click and release on the board outline at the very top of the circle and move your mouse to the first grid point above the origin. The origin will be at the center of you circle.
Now that you have your round board you will need to create your slots. If the slot is > .07" wide and long you can use overlapping non-plated drill holes to create the slot. We will drill these holes so it may be a rough slot. If you can't live with slot created using drills or if your slot width and/or length is .070 or less you will need to order through the Full Feature service at the http://www.sunstone.com website. If ordering through the Full Feature service you can draw your slots using the polygon drawing tools. The slots should be placed on the mechanical layer and please include additional notes on the mechanical layer describing, in as much detail as possible, what you would like fabricated.
Please feel free to contact support if you have any questions.