A small base with a hole to mount a 6x3 mm round magnet.

It's modeled to be used with this https://www.printables.com/de/model/542796-traffic-cone/comments traffic cone sized to 50 mm height.

My magnets were a bit less than 3 mm thick, so I modeled the hole accordingly. Hole depth is 2.8 mm and is chamfered. To mount a magnet, I put a drop of UV activated glue into the hole and push the magnet inside. The magnet squeezes the glue up and fills the chamfer gap.

The cone can be glued to the base with superglue.

I printed them in PLA with the magnet mounting hole facing up, manual supports for the “roof” and PETG as the top support interface material.

0.2 mm layers, 0.4 mm nozzle.