Quad Lock to Peak Design SlimLink adapter plate
An adapter puck with a Quad Lock style four-lug pattern on one face and a Peak Design SlimLink style square boss on the other, so a phone in a Peak Design Everyday case can use Quad Lock bike and car mounts you already own. The lug side is about 37 mm across and 4 mm tall to twist into the mount, and the SlimLink boss copies the square recess in the case with pockets for four 6 x 2 mm disc magnets glued in for retention. The disc is 6 mm thick, prints flat, and a 0.2 mm clearance keeps the twist firm.
Both interfaces have tight tolerances and both brands have revised them, so a downloaded adapter may fit neither of yours. In SpeakCAD you type the measurements from your own case and mount, preview the adapter free in the browser, refine the lug fit in the chat, then download the STL.
Create a 45 mm diameter, 6 mm thick adapter disc with a Quad Lock style four-lug boss 37 mm across and 4 mm tall on one face, and a Peak Design SlimLink style square boss 24 x 24 x 3 mm on the other with four 6 x 2 mm magnet pockets and 0.2 mm clearance.