Our bunny was just a little to short for the gap under our door, and PLA slips easily on tile. So we gave her a little base to lift her up and give her a little more traction. These parts are based on the Bunny Rabbit Pulling Carrot Doorstop model by CaptObvious.
This is printed in Flexfill 98a. With 0.2mm layers and a 0.6mm nozzle it took about 3 hours to print. Flexible materials print very slowly. Super glue seems to be holding it all together well so far. I clamped it in a (printed) vise while it set.
This STL file is 10mm tall, which should be more than enough for most door gaps. The photos show a 5mm printed height. There is plenty of software out there that should be able to do a basic plane cut so that you can choose the exact height you need without needing any complicated software. Your slicer may even have a plane cut feature.
Prusa Flexfill 98a
Bonus points: print on a powder coated (textured) print bed for better grip on tile.
Super glue the parts together, and clamp in a vise.