A practical approach is to suspend or rig the watch rather than rest it in putty. Community suggestions that fit this well:

• Build a simple support frame from PVC, wood sticks, or even a bent metal hanger.
• Hang the watch with thin nylon thread or cotton thread, using paper clips or wire as small hooks/supports.
• Use wire inside or around the strap to shape it consistently, especially if you want the band to appear naturally open.
• A small box or hidden support can also work as a base, with wires helping hold the strap in position.

For repeatable results, make one rig sized for your shot and mark the placement in your lightbox so each watch sits at the same angle. Thin supports are easier to clone out later than bulky putty. Nylon thread is often the least visible option, and paper clips/wire are useful for fine adjustment.

You may still need minor retouching in Photoshop to remove threads, wires, or clips, but this method usually gives cleaner, more consistent results than plasticine alone.