The holder can be printed from any material. No supports are necessary when the model is placed on the build plate with the foot facing down. A layer height of approx. 0.15mm is recommended.

The upper hole is meant to be used with a FlexMount20 Adapter for Tesla:

https://www.audiotec-fischer.de/helix/lautsprecher/compose/flexmounts/cfmk20-tes-1