The best way to orient a wall thickness 3D model is aligning its primary walls with the intended manufacturing (e.g., 3D printing build plate) or real-world use axis to preserve structural strength.
This ensures the wall’s thickness direction (like vertical for load-bearing walls) matches how the model will be made or used, preventing weak layers (in 3D printing) or misaligned load distribution.
For 3D printing, place the largest flat wall face on the build plate—most slicer tools let you preview orientation impacts on support and strength to adjust quickly.