I have tried placing a flat tile-like rock on the normal laying spot. However, the female clownfish was able to either move the rock away, or ignore it and continue laying the eggs on the large rock.
The strange thing is that in the past, the clownfish used to lay the eggs on the flat rock. Then, they suddenly moved to the larger rock. I'm not exactly sure why this happened saying that there was no change in the rock arrangement or other tank conditions.
I have not tried using flower pots yet. Is there a reason that some clownfish are attracted to lay their eggs in flower pots? I have a piece of artificial life rock that has a similar shape that I could try to use.
Thank you to everyone for all the advice. I really appreciate it.