Magnetic (or not) espresso filter holder

Requires a magnet.  You can use the prusaslicer solids to modify the magnet size and shape.  Designed for 58mm filters, it could be scaled for others.  Bottom is open for drips. Print vertical with a brim, set a pause to drop in the magnet.

If your magnet is smaller or the holder moves too much, apply a thin coating of rubber cement to the back and let dry before remounting.

Or, just double sticky tape it on.