Making small (<20mm) PCBs

I’m hoping to make a LED holder PCB which is a 13.5mm diameter circle. The forum won’t let me post an off-site link, but if you google for “ebay 260944856033” you’ll find a LED PCB for sale which is very close to what I’m building.

However on the Fusion PCB Service page, you request the following:

I can’t make the card larger for my application. Making a larger card that I can snap one of these cards out of violates your “no slots” rule. Any suggestions for how I should proceed?

I don’t know for sure, but it says you can make multiple boards (up to 5) on the same master board, you just can’t have them put a slot or multiple holes.
you’d need to cut the board yourself with a saw or dremmel.