Different qualities of finish depending on how much time you have to spend on it.
Some ideas I have:
Quickest, but roughest – metal wire, with fabric draped and glued/sown over.
Carved block of material; styrofoam; eva,
Stacked layers of foam core, cardboard, white card, etc
3D printed structure, fabric over
3D print the whole thing,
3D print pen, but that takes skill and patience
Because its just a model you can get away with some stuff. For curvy organic models I usually just used “terraced” layers of foam core. If anything is unclear I can try and find an example from google images to link you.
