Many thanks for your consideration.
In the attached file, I have decided to omit the "F1:f10" face. To achieve this, I selected the face and applied the "Geometry/Extrude Face". However, I have observed that the result of this operation is a duplicate shape overlaying it.
Could you please provide me with instructions or guidance on how to properly delete the "F1:f10" face and resolve the issue?
What precisely do you mean by you want to "omit" a face.
The FEATool geometry engine only works on enclosed solids in 3D. So if you would delete a face from a cube it would have a hole which is not permitted. To work with free surfaces in 3D you can use other CAD software, like for example freecad or fusion360, after which you can import the CAD model in STEP or IGES format. Note, that imported geometries into FEATool must be enclosed, no holes in the geometry objects are allowed.