thats what my gecko has been doing. just put the water dish in the aquarium for an hour or so a day a couple times a day so she doesnt have time to do that.
and maybe then she'll use the lay box
This may sound abit cruel but ive heard of ppl doing this...Try "locking" your gecko in a large lay box right b4 uthink shes gunna lay, make sure theres air holes tho