If you have a recent generation dewalt router like DWP611, DWP616, DWP618 which all have the mounting hole spacing of 2.4 inches on center you can download the subbase from here: https://www.printables.com/model/949098-dewalt-router-circle-jig
The author remixed this model.
Added chamfers and roundovers in most corners.
Replaced the mounting holes with a 105 mm diameter slot that allows the router to sit on, instead of being screwed in.