However, I am struggling with the exact workflow to implement this raw SPICE model into my 3D design. Could someone kindly provide a step-by-step guide on the following:

1. Importing the Model: How do I properly link this SPICE file to the physical gap between my copper traces in the 3D environment? Should I use the Schematic (CST Design Studio) co-simulation, or is there a way to embed it directly into a 3D Lumped Element?
2. Setting the States: How do I correctly define the "ON" state (forward bias) and the "OFF" state (reverse bias) using this imported model so I can simulate my different phase combinations?
3. Stability: I have read that SPICE co-simulation can sometimes struggle or cause crashes with the 3D Frequency Domain solver. Are there any specific settings I should check to ensure the simulation remains stable?

I would be incredibly grateful for any advice or step-by-step instructions. Thank you so much in advance for your time and help!

Best regardsSpiceCST Studio Suite 

SPICE model 
3D design 
copper traces 
phase combinations 
3D Frequency Domain solver 
step-by-step guide 
Schematic (CST Design Studio) co-simulation 
3D Lumped Element embedding 
stability settings 
3D environment 
simulation stability 
defining ON/OFF states 
linking SPICE to physical gap